feat(auth): add JSpecify Null annotations to Auth

[nnicolee]

tba

[gemini-code-assist]

Code Review

This pull request introduces JSpecify nullness annotations (@NullMarked and @nullable) across several modules, including GAX and Google Cloud Bigtable, and updates tests to configure Mockito mocks to ignore annotations. The reviewer feedback highlights several improvement opportunities, such as correcting a potentially unsafe @nullable annotation on a builder constructor parameter to avoid NullPointerExceptions, and ensuring that the previousThrowable parameters in retry algorithms are explicitly marked as @nullable to handle successful attempts where no exception is thrown.

[gemini-code-assist]

Annotating stubSettings as @Nullable suggests that null is a valid argument. However, if stubSettings is null, calling methods like getQuotaProjectId() or getWatchdogProvider() on this builder will result in a NullPointerException because they dereference stubSettings without a null check. If stubSettings must not be null, it should not be annotated with @Nullable, and ideally, a null check like Preconditions.checkNotNull(stubSettings) should be added.

[gemini-code-assist]

In a @NullMarked class, previousThrowable should be annotated with @Nullable because on successful attempts (e.g., during polling or when checking if retries should continue after a success), previousThrowable can be null.

Suggested change

	*/
	@Nullable Throwable previousThrowable,

[gemini-code-assist]

In a @NullMarked class, previousThrowable should be annotated with @Nullable because on successful attempts (e.g., during polling or when checking if retries should continue after a success), previousThrowable can be null.

Suggested change

	Throwable previousThrowable,
	@Nullable Throwable previousThrowable,

[gemini-code-assist]

In a @NullMarked class, previousThrowable should be annotated with @Nullable because on successful attempts (e.g., during polling or when checking if retries should continue after a success), previousThrowable can be null.

Suggested change

	Throwable previousThrowable,
	@Nullable Throwable previousThrowable,

[gemini-code-assist]

In a @NullMarked class, previousThrowable should be annotated with @Nullable because on successful attempts (e.g., during polling or when checking if retries should continue after a success), previousThrowable can be null.

Suggested change

	Throwable previousThrowable,
	@Nullable Throwable previousThrowable,

[sonarqubecloud]

Quality Gate failed for 'gapic-generator-java-root'

Failed conditions
B Maintainability Rating on New Code (required ≥ A)
C Reliability Rating on New Code (required ≥ A)

See analysis details on SonarQube Cloud

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[sonarqubecloud]

Quality Gate failed for 'gapic-generator-java-root'

Failed conditions
0.0% Coverage on New Code (required ≥ 80%)
B Maintainability Rating on New Code (required ≥ A)
C Reliability Rating on New Code (required ≥ A)

See analysis details on SonarQube Cloud

💡 Need a hand with PR review? Try Gitar by Sonar!