Within T366989: Edits made via Special:CommunityConfiguration should have a CommunityConfiguration tag attached, @Michael added support for the CommunityConfiguration edit tag. In that task, CommunityConfiguration only started to add its own edit tag unconditionally, and it does not allow anyone else to specify other tags to be added.
While migrating structured mentor list to MediaWiki-extensions-CommunityConfiguration as part of T367575: Structured Mentor list should make use of CommunityConfiguration extension, I realised we have the mentor list change edit tag as well. We should continue having that tag, as it is useful as an explanation of why are non-admin users editing in NS_MEDIAWIKI.
To make that possible, we need to allow client extensions of MediaWiki-extensions-CommunityConfiguration to provide their own edit tags, which will then be added to the edits. This is the scope of this task.