This was added specifically for `ModDifficultyAdjust`, but turned out to
be more of a headache than we expected. We have since removed usage and
would hope that this is not required by any other mods.
Opting for complete removal rather than obsoletion, as we discovered
this was already broken in multiple cases, with fixes being quite
logically complex.
If you happen to be a ruleset developer relying on this, open an issue
and we'll talk you through a better approach (or check what
`ModDifficultyAdjust` is doing now for an example).
Closes#13847.
I think we can probably get some test coverage of this if required, but
needs a bit of thought (basically an error needs to be thrown during the
multiplayer client portion of the join procedure, after `CurrentRoom` is
non-null but before the join completes).
Manual testing on password branch (#13861) is possible since it
currently errors due to missing method on the live/dev servers.
- Create game, which will fail with `MethodNotExists`.
- Note the fields on the settings screen are emptied.
- Fill fields again and press create game (crash).