sonar failers due to 401

[zhumin8]

all sonar builds has been failing since Dec2.
https://github.com/googleapis/google-auth-library-java/actions/runs/12131139021/job/33822744230

Error:  Failed to execute goal org.sonarsource.scanner.maven:sonar-maven-plugin:5.0.0.4389:sonar (default-cli) on project google-auth-library-parent: Error status returned by url [https://api.sonarcloud.io/analysis/jres?os=linux&arch=x86_64]: 401 -> [Help 1]

similar issue in sdk-platform-java: googleapis/sdk-platform-java#3369

[meltsufin]

Added SONAR_TOKEN and validated the workflow working in #1592.

[lqiu96]

Re-opening this as it seems to still fail: https://github.com/googleapis/google-auth-library-java/actions/runs/12282128891/job/34272653159?pr=1590

Min mentioned above that this seems to be flaky in sdk-platform-java as well: googleapis/sdk-platform-java#3369

[lqiu96]

This is not a flaky issue, but rather an issue when PRs are raised from forks. Fork PRs do not have access to secrets and cannot use the SONAR_TOKEN secret.

We have disabled sonar from running when the PR comes from Forks. For now, the workaround way to test with sonar is when PRs come in from forks:

1. Raise the PR to a branch
2. Raise a PR from the branch in above step to main

"Fixed" in #1606