Add fallback for Follower post-meta

[pfefferle]

We recently migrated the followers post-type to use _activitypub_follower instead of _activitypub_user_id to also support followings using the same mechanism.

It seems that the migration wasn't properly run on every installation, so this PR adds fallback support for _activitypub_user_id until we found and fixed the issue.

Fight the symptoms ✊

😔

Proposed changes:

• Add fallback support for _activitypub_user_id

Other information:

• [ ] Have you written new tests for your changes, if applicable?

Testing instructions:

• Go to '..'

Changelog entry

• [X] Automatically create a changelog entry from the details below.

Changelog Entry Details

Significance

• [X] Patch
• [ ] Minor
• [ ] Major

Type

• [ ] Added - for new features
• [ ] Changed - for changes in existing functionality
• [ ] Deprecated - for soon-to-be removed features
• [ ] Removed - for now removed features
• [X] Fixed - for any bug fixes
• [ ] Security - in case of vulnerabilities

Message

Improved compatibility with older follower data.