add name checking

[Papayapaya]

cleans up names in make_user, removing invisible/weird whitespace characters. (idk whats going on with gitignore and cargo lock but lmk if i need to chage/remove those)

[quantumish]

Thanks for moving the .gitignore and adding whitespace handling!

Blocking feedback:

• I think this logic might be better suited to be its own function, which is then called by other methods whenever they take user input for names (e.g. making group chats, channels, etc.)
• Would this maybe be better done with a call to filter() as that'd prevent a maximum name length (and maybe be a bit cleaner)? On the other hand, it does broadly make sense to have some sort of max length as a 2GB long name for a group chat would cause problems. Open to pushback here.

Nitpicks (not blocking):

• It'd be nice if you could format the whitespace array so it isn't all on one line
• I don't know what unicode codepoints those are off the top of my head, but would they be covered by the char::is_whitespace() method?
• Default name of an empty string is also not preferred (I think it should probably just fail if you try to make a bad name with no salvageable characters).