test: adds integration tests for workload identity federation

[lsirac]

A setup script workloadidentityfederation-setup.sh is added to make the workload identity pool configuration changes on the current project, if needed. The setup script only needs to be run once on a project (already ran).

[elharo]

Tests fail on windows:

Error: Tests run: 2, Failures: 0, Errors: 2, Skipped: 0, Time elapsed: 0.052 s <<< FAILURE! - in com.google.auth.oauth2.ITWorkloadIdentityFederationTest
Error: com.google.auth.oauth2.ITWorkloadIdentityFederationTest.identityPoolCredentials Time elapsed: 0.046 s <<< ERROR!
java.lang.NullPointerException
at com.google.auth.oauth2.ITWorkloadIdentityFederationTest.getServiceAccountKeyFileAsJson(ITWorkloadIdentityFederationTest.java:247)
at com.google.auth.oauth2.ITWorkloadIdentityFederationTest.setup(ITWorkloadIdentityFederationTest.java:93)

Error: com.google.auth.oauth2.ITWorkloadIdentityFederationTest.awsCredentials Time elapsed: 0 s <<< ERROR!
java.lang.NullPointerException
at com.google.auth.oauth2.ITWorkloadIdentityFederationTest.getServiceAccountKeyFileAsJson(ITWorkloadIdentityFederationTest.java:247)
at com.google.auth.oauth2.ITWorkloadIdentityFederationTest.setup(ITWorkloadIdentityFederationTest.java:93)

[chingor13]

Tests fail on windows:

The windows and unit test failures are because these tests are integration tests that we only want to run in certain cases (need credentials and need to run on Kokoro).

[codecov]

Codecov Report

Merging #581 (2beb042) into master (5c7deec) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master     #581      +/-   ##
============================================
+ Coverage     83.45%   83.49%   +0.04%     
- Complexity      594      599       +5     
============================================
  Files            41       42       +1     
  Lines          2695     2708      +13     
  Branches        286      288       +2     
============================================
+ Hits           2249     2261      +12     
- Misses          303      304       +1     
  Partials        143      143              

Impacted Files	Coverage Δ	Complexity Δ
...tp/java/com/google/auth/oauth2/AwsCredentials.java	93.26% <100.00%> (-0.91%)	15.00 <5.00> (-1.00)
...google/auth/oauth2/ExternalAccountCredentials.java	97.76% <100.00%> (+0.14%)	29.00 <5.00> (+3.00)
...om/google/auth/oauth2/IdentityPoolCredentials.java	86.17% <100.00%> (+0.14%)	12.00 <0.00> (ø)
.../google/auth/oauth2/SystemEnvironmentProvider.java	100.00% <100.00%> (ø)	3.00 <3.00> (?)

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[generated-files-bot]

Warning: This pull request is touching the following templated files:

• .kokoro/nightly/integration.cfg
• .kokoro/presubmit/integration.cfg

[chingor13]

In hindsight, we should have made these protected constructors accept only the Builders to avoid bloating all these constructor overloads.