feat: Adds support for user defined subject token suppliers in AWSCredentials and IdentityPoolCredentials (#1336)

* feat: adds programmatic auth credentials for identity pool and aws credential types

* feat: add quality of life improvements for building external account credentials in code.

* fix: formatting

* fix: add formatting

* Adds @CanIgnoreReturnValue on new builder methods

* Change test for impersonated credentials

* formatting

* adding id_token type

* formatting

* Update oauth2_http/java/com/google/auth/oauth2/AwsCredentials.java

Co-authored-by: Leo <39062083+lsirac@users.noreply.github.com>

* PR comments

* Added header value constants

* updating java doc

* adding integration tests

* fix tests

* fix tests, add javadoc, and format

* PR review comments

* Update oauth2_http/java/com/google/auth/oauth2/AwsCredentials.java

Co-authored-by: Leo <39062083+lsirac@users.noreply.github.com>

* PR comments

* changing to aws_region instead of region to clarify usage and keep region available for future use.

* Adding Aws Security Credential Providers

* Adding identity pool providers

* PR comments

* fix test

* refactoring to expose rename provider to supplier and expose it publicly

* formatting

* updating codeowners

* make subject token supplier interface public

* Making AwsSecurityCredentials public and change name to sessionToken

* lint

* fix tests

* lint

---------

Co-authored-by: Leo <39062083+lsirac@users.noreply.github.com>

Author: aeitzman

.github/CODEOWNERS

@@ -18,32 +18,37 @@ samples/**/*.java       @googleapis/java-samples-reviewers
 samples/snippets/generated/       @googleapis/yoshi-java
 
 # 3PI-related files and related base classes - joint ownership between googleapis-auth and aion-sdk
-oauth2_http/java/com/google/auth/oauth2/ActingParty.java                      @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/AwsCredentials.java                   @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/AwsDates.java                         @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/AwsRequestSignature.java              @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/AwsRequestSigner.java                 @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/AwsSecurityCredentials.java           @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/CredentialAccessBoundary.java         @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/DefaultCredentialsProvider.java       @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/DownscopedCredentials.java            @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/EnvironmentProvider.java              @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/ExecutableHandler.java                @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/ExecutableResponse.java               @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/ExternalAccountCredentials.java       @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/GoogleCredentials.java                @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/IdentityPoolCredentials.java          @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/ImpersonatedCredentials.java          @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/OAuth2Credentials.java                @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/OAuth2CredentialsWithRefresh.java     @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/OAuthException.java                   @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/PluggableAuthCredentials.java         @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/PluggableAuthException.java           @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/PluggableAuthHandler.java             @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/StsRequestHandler.java                @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/StsTokenExchangeRequest.java          @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/StsTokenExchangeResponse.java         @googleapis/googleapis-auth @googleapis/aion-sdk
-oauth2_http/java/com/google/auth/oauth2/SystemEnvironmentProvider.java        @googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/ActingParty.java                      		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/AwsCredentials.java                   		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/AwsSecurityCredentialsSupplier.java   		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/AwsDates.java                         		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/AwsRequestSignature.java              		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/AwsRequestSigner.java                 		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/AwsSecurityCredentials.java           		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/CredentialAccessBoundary.java         		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/DefaultCredentialsProvider.java       		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/DownscopedCredentials.java            		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/EnvironmentProvider.java              		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/ExecutableHandler.java                		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/ExecutableResponse.java               		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/ExternalAccountCredentials.java       		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/FileIdentityPoolSubjectTokenSupplier.java 	@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/GoogleCredentials.java                		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/IdentityPoolCredentials.java          		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/IdentityPoolSubjectTokenSupplier.java		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/ImpersonatedCredentials.java          		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/InternalAwsSecurityCredentialsSupplier.java	@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/OAuth2Credentials.java                		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/OAuth2CredentialsWithRefresh.java     		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/OAuthException.java                   		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/PluggableAuthCredentials.java         		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/PluggableAuthException.java           		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/PluggableAuthHandler.java             		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/StsRequestHandler.java                		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/StsTokenExchangeRequest.java          		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/StsTokenExchangeResponse.java         		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/SystemEnvironmentProvider.java        		@googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/java/com/google/auth/oauth2/UrlIdentityPoolSubjectTokenSupplier.java	@googleapis/googleapis-auth @googleapis/aion-sdk
 oauth2_http/javatests/com/google/auth/AwsCredentialsTest.java                           @googleapis/googleapis-auth @googleapis/aion-sdk
 oauth2_http/javatests/com/google/auth/AwsRequestSignerTest.java                         @googleapis/googleapis-auth @googleapis/aion-sdk
 oauth2_http/javatests/com/google/auth/CredentialAccessBoundaryTest.java                 @googleapis/googleapis-auth @googleapis/aion-sdk
@@ -55,6 +60,7 @@ oauth2_http/javatests/com/google/auth/ITDownscopingTest.java
 oauth2_http/javatests/com/google/auth/ITWorkloadIdentityFederationTest.java             @googleapis/googleapis-auth @googleapis/aion-sdk
 oauth2_http/javatests/com/google/auth/IdentityPoolCredentialsTest.java                  @googleapis/googleapis-auth @googleapis/aion-sdk
 oauth2_http/javatests/com/google/auth/ImpersonatedCredentialsTest.java                  @googleapis/googleapis-auth @googleapis/aion-sdk
+oauth2_http/javatests/com/google/auth/InternalAwsSecurityCredentialsSupplierTest.java	@googleapis/googleapis-auth @googleapis/aion-sdk
 oauth2_http/javatests/com/google/auth/MockExternalAccountCredentialsTransport.java      @googleapis/googleapis-auth @googleapis/aion-sdk
 oauth2_http/javatests/com/google/auth/MockStsTransport.java                             @googleapis/googleapis-auth @googleapis/aion-sdk
 oauth2_http/javatests/com/google/auth/OAuth2CredentialsTest.java                        @googleapis/googleapis-auth @googleapis/aion-sdk
@@ -65,4 +71,4 @@ oauth2_http/javatests/com/google/auth/PluggableAuthExceptionTest.java
 oauth2_http/javatests/com/google/auth/PluggableAuthHandlerTest.java                     @googleapis/googleapis-auth @googleapis/aion-sdk
 oauth2_http/javatests/com/google/auth/StsRequestHandlerTest.java                        @googleapis/googleapis-auth @googleapis/aion-sdk
 oauth2_http/javatests/com/google/auth/TestEnvironmentProvider.java                      @googleapis/googleapis-auth @googleapis/aion-sdk
-README.md                                                                               @googleapis/googleapis-auth @googleapis/aion-sdk
+README.md                                                                               @googleapis/googleapis-auth @googleapis/aion-sdk