As a blocker to T108557 going any further...
#mediawiki-extensions-urlshortener is wanted by various projects, and is half deployed on Wikimedia Wikis in a readonly state. There is no owner of the extension or it's deployment, as such, it's currently stuck.
https://www.mediawiki.org/wiki/Extension:UrlShortener was created as response to https://www.mediawiki.org/wiki/Requests_for_comment/URL_shortener#Tim.27s_implementation_suggestion
It has been installed in a readonly mode for the last 2 years - https://github.com/wikimedia/operations-mediawiki-config/commit/6696f1e5dad6d2a02c40c4464f47d6e270855879