fix: cancel scheduled notification when reverting a post to draft.

[marclucraft]

One Line Summary

fix: Cancel scheduled notification when reverting a post to draft. Updated version to 3.9.1

Motivation

Customer follow up via Support

Previously, reverting a scheduled post to Draft or Pending Review left the
corresponding OneSignal notification queued — it would still fire at the
original scheduled time even though the post was no longer going to publish.

Scope

• Affected: Scheduled posts (future status) that are reverted to Draft or
  Pending Review before their publish time.
• Not affected: Posts being published, posts having their scheduled date
  changed via quick-edit (existing behaviour unchanged), post deletion/trash,
  v2 legacy code, JS/CSS behaviour, any other status transitions.

Testing

Manual

1. Install the plugin with a valid OneSignal App ID and REST API key.
2. Create a new post, set the publish date to tomorrow, check Send push
   notification, and save as Scheduled.
3. Confirm a scheduled notification appears in the OneSignal dashboard with the
   correct send time.
4. Reopen the post in WordPress, switch its status to Draft, and update.
5. Expected: The notification is cancelled in the OneSignal dashboard and no
   push is delivered at the original scheduled time.
6. Repeat step 4 using Pending Review — same expected outcome.
7. Verify the inverse: trash a scheduled post still cancels the notification
   (regression check on the shared helper).
8. Verify: changing a scheduled post's date via quick-edit still cancels and
   re-creates the notification (regression).

Test in both Classic editor and Block (Gutenberg) editor.
WordPress 6.x+, PHP 7.4+.

Unit / Integration

Three new integration tests added to tests/integration/TestAPIIntegration.php:

• test_cancel_notification_when_scheduled_post_reverts_to_draft — verifies the
  DELETE API call is made and post meta is cleared on a future → draft transition.

• test_no_cancellation_when_no_notification_stored_on_draft_revert — verifies
  no HTTP request is made when there is no stored notification ID.

• test_no_cancellation_for_disallowed_post_type_on_draft_revert — verifies the
  post-type guard prevents cancellation for unregistered post types.

• composer test passes locally

Affected code checklist

• PHP plugin code (v3/)
• v2/ legacy code
• JS / CSS assets
• Build / CI
• Tests
• Documentation (README, readme.txt, etc.)

Checklist

• Code follows existing style in the touched files
• Tested manually in the relevant editor(s)
  • Gutenberg/Block editor
  • Classic editor
• No new lint or test errors introduced
• Linear ticket / GitHub issue linked above
• readme.txt and plugin version bumped if user-facing (release PRs only)

[sherwinski]

Thanks @marclucraft, let me give this a test locally and review before moving to merge.