[BUG]: Having a user called "silent"/"silently" in the server confuses silent contact

[Erisa]

Bot Version

3.10.3

How are you hosting Modmail?

Heroku

Error Logs

https://haste.erisa.uk/agiquq.apache

Screenshots

Additional Information

If a user in the server is called silent or silently then the flow ?contact @user silent or ?contact @user silently respectively will become confused and a open a non-silent thread with both @user and the user called silent or silently.

If unnoticed this results in the contact not being silent (Shows the recipient who opened the thread) and the silent/silently user receiving all of the modmail communication in that thread.

Reproduction is somewhat simple, just have a user named silent or silently in the server and use ?contact @user silent against a different user.

From my understanding this appears to happen because the users argument will do a "greedy" match against any users it can find before getting to the silent/silently argument after it, causing the silent/silently to be dropped and the matching user to be added to the list in its place.

https://github.com/kyb3r/modmail/blob/be14cca89742cd691f6b91f0d0931a074ad81e3b/cogs/modmail.py#L1333-L1340

[ghost]

Can reproduce on v4 also