User may be able to create an custom short URL. The short URLs can still be disabled by stewards, and no automatic short URL identical to them will be generated.
Technically, we need a new database table to store them (see also T221016#5358449).
To reduce the abuse potential, the followings may be considered (not mandatory):
- Creation of custom short URL may be limited to a specific user group (e.g. autoconfirmed user)
- There should be a special page to list all newly-created short URL (T228779: Create a special page to list all short URLs)
- Creation of custom short URL may be logged, while other short URL creations are still anonymous (this should be clearly explained in the interface)