To add to the above here the first PR from my message above.
Reviews and opinions welcome! Fixed #13376: Added kwargs argument to messages API to allow extension of functionality to the Storage & Message class. by nanorepublica · Pull Request #18332 · django/django · GitHub
For comparison the initial PR for this ticket is here: Fixed #13376: Added restrictions to messages to control when they are hidden. by nanorepublica · Pull Request #18286 · django/django · GitHub