Powerlevel allows illegal characters in the user identifier

[MichaelSasser]

Describe the bug
!mjolnir powerlevel does not check for illegal characters in the user identifier. If I remember that correctly, only lowercase letters, numbers, underscores, and dashes are allowed.

To Reproduce
It is possible to set the powerlevel using a user identifier with illegal characters. (Tested with mjolnir v1.2.1)

1. !mjolnir powerlevel @FooBarBaz:matrix.org 50 (Uppercase letters are not allowed, I haven't tested other characters)
2. See room roles & permissions

Expected behavior
The bot should throw an error.

[tulir]

Note that uppercase letters are allowed in historical user IDs (meaning there are real users with uppercase user IDs), and arbitrary unicode is allowed in user IDs over federation (meaning a server admin could create user IDs with any unicode characters and other servers will accept them). See also: matrix-org/matrix-spec-proposals#2828

[MichaelSasser]

Thanks for your detailed response. Since this is a feature, I close the issue.