[pfefferle]

Fixes #4064

Proposed changes:

• Mention::filter_activity_object() linked mentions in summary, but not in summaryMap, which is built earlier from the plain summary. So the two differed, and GoToSocial showed the mention as @user <https://…>.
• The maps hold the same text in other languages, so they should get the same links. Mention, Hashtag and Link now also link every value in summaryMap and contentMap. This also covers translations that plugins add through activitypub_transform_set_summary_map and activitypub_transform_set_content_map.
• Hashtag and Link keep the is_actor() check for summaryMap, the same as for summary, so the summary of a post stays plain text (Improve summary generation #2063).

Other information:

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

Testing instructions:

• Publish a post with a title that mentions someone, for example @searls@mastodon.social nails it….
• Open the post with ?activitypub (or fetch it with Accept: application/activity+json).
• summary and the value in summaryMap are the same, both with the linked mention.
• contentMap matches content.

Changelog entry

• Automatically create a changelog entry from the details below.

The entry is in .github/changelog/fix-mention-summary-map.