chore: standardize/update release please config

[toddbaert]

Standardizes this repo's release-please setup. Part of open-feature/community-tooling#128.

• pin googleapis/release-please-action@45996ed…307cf7 # v5
• token: ${{ secrets.RELEASE_PLEASE_ACTION_TOKEN }}
• signoff configured in release-please-config.json (removes deprecated command/default-branch/signoff inputs); fixes DCO on release PRs
• release gate uses the always-emitted, monorepo-safe plural releases_created via fromJSON(... || false)
• add a concurrency guard to serialize release-please runs

Single signed-off commit; no changes to custom publish/build steps.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Advanced

Run ID: e47044d1-5f7e-44d9-937f-38d443ba6680

📥 Commits

Reviewing files that changed from the base of the PR and between acc424b and 87411e5.

📒 Files selected for processing (1)

• .github/workflows/release-please.yml

Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review.

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📝 Walkthrough

Walkthrough

The release-please workflow now groups runs by Git reference. It sets cancel-in-progress to false.

Changes

Release workflow

Layer / File(s)	Summary
Configure workflow concurrency .github/workflows/release-please.yml	The workflow groups runs by Git reference and sets cancel-in-progress to false.

Estimated code review effort: 2 (Simple) | ~7 minutes

Suggested reviewers: aepfli

Merge Risk: ⚪ Minimal · up to 87411

The concurrency guard does not lose release work because later main-branch runs process accumulated commits. No actionable merge risk remains.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description directly explains the Release Please configuration changes, including the concurrency guard and related workflow updates.
Title check	✅ Passed	The title clearly identifies the primary change as standardizing and updating the Release Please configuration.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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