Comment: Send announce for all new comments

[pfefferle]

Supersedes #1515 and fixes #1001

Proposed changes:

• Stores the Activity in the Comment-Meta, because we have to get sure, that the comment will be approved or not before announcing it
• Hook into approve process, to late federate the Announce

Other information:

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

Testing instructions:

• Apply this change to a WP test site that's accessible online.
• Comment on a post from a fediverse instance of your choice.
• Check the Outbox and make sure it created an Announce activity.

Changelog entry

• Automatically create a changelog entry from the details below.

Changelog Entry Details

Significance

• 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
• Fixed - for any bug fixes
• Security - in case of vulnerabilities

Message

Incoming interactions create an Announce activity so other instances get notified about it.