Add update_apps_cdn_build_metadata action

[iangmaia]

Fixes AINFRA-2102

Summary

• Adds a new update_apps_cdn_build_metadata Fastlane action that updates metadata (e.g. visibility) of an existing build on the Apps CDN without re-uploading the file
• Uses the WordPress.com REST API (POST /rest/v1.1/sites/{site_id}/posts/{post_id}) to update taxonomy terms
• Supports updating visibility (:internal / :external) and post_status (publish / draft)
• This enables a two-phase release flow: upload builds as Internal during finalize, then flip to External at publish time

Context

The companion Studio PR uses this action in its publish_release lane.

The existing upload_build_to_apps_cdn action cannot be used to change visibility because visibility is part of the dedup matching criteria in the CDN plugin — re-uploading with a different visibility creates a new build rather than updating the existing one.

Test plan

• Unit tests added and passing (bundle exec rspec spec/update_apps_cdn_build_metadata_spec.rb)
• Manual test: call the action against a real CDN build post to verify the WPCOM API accepts terms[visibility] updates

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds a new Fastlane action to update metadata on an existing Apps CDN build post via the WordPress.com REST API, enabling a two-phase release flow (upload internal → later flip to external without re-upload).

Changes:

• Introduces update_apps_cdn_build_metadata Fastlane action that POSTs updates to an Apps CDN build post (visibility/status).
• Adds RSpec coverage for successful updates, validation, and error handling.
• Documents the new action in the Trunk changelog.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
spec/update_apps_cdn_build_metadata_spec.rb	Adds unit tests for the new action’s request shaping, validation, and error cases.
lib/fastlane/plugin/wpmreleasetoolkit/actions/common/update_apps_cdn_build_metadata.rb	Implements the new Fastlane action that updates build metadata via WPCOM REST API.
CHANGELOG.md	Adds a Trunk “New Features” entry for the new action.

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