[mwbrooks]

This pull request posts each published GitHub Release to our internal release announcements channel, so maintainers no longer share Java SDK releases by hand. It uses the same webhook and message shape as the Slack CLI and Node SDK release workflows.

• A new release-announcement.yml workflow runs on release: published and skips prereleases and forks.
• It's a separate workflow because release.yml also publishes snapshots, and the GitHub Release is created by hand after the Maven publish.
• The maintainers guide now says to check for the announcement, not to post one.

Testing

• Confirmed the SLACK_RELEASE_ANNOUNCEMENTS_WEBHOOK_URL org secret is shared with this repo.
• On the next release, confirm the announcement posts after the GitHub Release is published.

Category (place an x in each of the [ ])

• bolt (Bolt for Java)
• bolt-{sub modules} (Bolt for Java - optional modules)
• slack-api-client (Slack API Clients)
• slack-api-model (Slack API Data Models)
• slack-api-*-kotlin-extension (Kotlin Extensions for Slack API Clients)
• slack-app-backend (The primitive layer of Bolt for Java)

Requirements

Please read the Contributing guidelines and Code of Conduct before creating this issue or pull request. By submitting, you agree to those rules.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.29%. Comparing base (01c1e74) to head (093fc48).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1671      +/-   ##
============================================
+ Coverage     73.28%   73.29%   +0.01%     
- Complexity     4653     4654       +1     
============================================
  Files           486      486              
  Lines         14654    14654              
  Branches       1524     1524              
============================================
+ Hits          10739    10741       +2     
+ Misses         3012     3011       -1     
+ Partials        903      902       -1     

Flag	Coverage Δ
jdk-14	73.29% <ø> (+0.01%)	⬆️

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[mwbrooks]

note: Confirmed the SLACK_RELEASE_ANNOUNCEMENTS_WEBHOOK_URL org secret is shared with this repo, so the workflow can post on the next release. 🔐

[mwbrooks]

note: This uses the same <repo> <tag> format as the Slack CLI announcement, so v1.53.0 would read java-slack-sdk v1.53.0. Happy to change it if we'd rather have something else, like the release name.