HADOOP-19851. Point S3A GCS docs to the hadoop-gcp connector

[johntomcat7408-cmyk]

Description of PR

This PR updates the S3A third-party-store documentation for Google Cloud
Storage to point users to Hadoop's hadoop-gcp gs: connector configuration
page instead of the external Dataproc connector page.

The existing S3A compatibility scenarios, configuration, limitations, and test
guidance remain unchanged. This is a documentation-only change: it does not
modify Java code, dependencies, public APIs, configuration defaults or
examples, endpoints, regions, or runtime behavior.

Jira: https://issues.apache.org/jira/browse/HADOOP-19851

HADOOP-19851 supplied the problem statement and requested direction. PR #8058
was reviewed only because it also changes this Markdown file; no unmerged code,
commit, or wording from that PR was reused. This patch was authored
independently against the current trunk baseline.

Contains content generated by Codex

How was this patch tested?

Environment: Windows x86_64, Eclipse Temurin 17.0.19, and the project Maven
Wrapper with Maven 3.9.15.

1. Installed the reactor artifacts required by the two affected site modules:

   .\mvnw.cmd --batch-mode --no-transfer-progress install `
     -pl ":hadoop-aws,:hadoop-gcp" -am "-P=-native-win" `
     "-DskipTests" "-DskipShade" "-DskipDocs"

   All 36 reactor projects completed successfully. This command skipped tests
   and was used only to prepare local site artifacts.

2. Ran the targeted site build twice, as required by BUILDING.txt:

   .\mvnw.cmd --batch-mode --no-transfer-progress site site:stage `
     -pl ":hadoop-aws,:hadoop-gcp" "-Preleasedocs,docs" `
     "-DstagingDirectory=<temporary-directory>" "-DgenerateReports=false"

   Both runs completed with BUILD SUCCESS. The generated
   third_party_stores.html contained
   ../../../hadoop-gcp/tools/hadoop-gcp/Configuration.html; resolving that
   href from the generated source page matched the generated
   Configuration.html file, which existed. The new gs: guidance was present
   and the old Dataproc connector link was absent.

3. Ran Apache Yetus 0.14.1 from an isolated baseline worktree:

   dev-support/bin/test-patch --branch=799ef577... \
     --basedir=<isolated-worktree> --patch-dir=<temporary-directory> \
     --git-offline --build-native=false --java-home=<JDK-17> <patch-file>
   

   Yetus reported +1 overall. The Hadoop personality classified the pure
   Markdown patch as nobuild, so this did not run Java compilation or tests.

4. git diff --check upstream/trunk...HEAD completed without errors.

The root-reactor aggregate site was not completed because the local environment
did not contain every artifact required by the full reactor; one Maven Central
request was also reset. The two affected modules' generated pages and their
cross-module href were verified directly. Java tests and object-store
integration tests are not applicable because the final diff changes no code,
configuration, endpoint, region, or runtime semantics.

For code changes:

• Does the title or this PR starts with the corresponding JIRA issue id (e.g. 'HADOOP-17799. Your PR title ...')?
• Object storage: have the integration tests been executed and the endpoint declared according to the connector-specific documentation?
  N/A: this patch changes documentation guidance only and does not change an object-store endpoint or runtime behavior.
• If adding new dependencies to the code, are these dependencies licensed in a way that is compatible for inclusion under ASF 2.0?
  N/A: no dependencies are added.
• If applicable, have you updated the LICENSE, LICENSE-binary, NOTICE-binary files?
  N/A: the change adds no dependency or third-party material requiring a license or notice update.

AI Tooling

If an AI tool was used:

• The PR includes the phrase "Contains content generated by "
  where is the name of the AI tool used.
• My use of AI contributions follows the ASF legal policy
  https://www.apache.org/legal/generative-tooling.html

[github-actions]

ℹ️ Cloud-AWS manual trigger instructions: S3A tests must be manually triggered for fork pull requests. A maintainer should:

• Confirm the PR does not contain risky changes to actions in .github/workflows and .github/actions.
• Approve workflows for this fork PR if prompted.
• Run Cloud-AWS workflow with pr_number=8639 (or via CLI: gh workflow run cloud_aws.yml -R apache/hadoop -f pr_number=8639)

fork head: johntomcat7408-cmyk/hadoop@1a1cf5256fdf

[hadoop-yetus]

🎊 +1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	13m 42s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 0s		codespell was not available.
+0 🆗	detsecrets	0m 0s		detect-secrets was not available.
+0 🆗	markdownlint	0m 0s		markdownlint was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
			_ trunk Compile Tests _
+1 💚	mvninstall	41m 32s		trunk passed
+1 💚	mvnsite	1m 15s		trunk passed
+1 💚	shadedclient	71m 42s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	0m 42s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	mvnsite	0m 43s		the patch passed
+1 💚	shadedclient	28m 0s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	asflicense	0m 36s		The patch does not generate ASF License warnings.
		116m 35s

Subsystem	Report/Notes
Docker	ClientAPI=1.55 ServerAPI=1.55 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-8639/1/artifact/out/Dockerfile
GITHUB PR	#8639
Optional Tests	dupname asflicense mvnsite codespell detsecrets markdownlint
uname	Linux d64e214d4b85 5.15.0-181-generic #191-Ubuntu SMP Fri May 22 19:09:02 UTC 2026 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / 1a1cf52
Max. process+thread count	635 (vs. ulimit of 10000)
modules	C: hadoop-tools/hadoop-aws U: hadoop-tools/hadoop-aws
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-8639/1/console
versions	git=2.43.0 maven=3.9.15
Powered by	Apache Yetus 0.14.1 https://yetus.apache.org

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