Usernamefilter - search if any username in a message violates the rules

[d-Rickyy-b]

Currently only one/the first username needs to be an allowed one, then the system can be tricked. This should be done by checking each entity/username and if one violates the rules, the filter should return True.

[d-Rickyy-b]

Might be best to use Message Entities - also see here (type = mention) for this, since the framework already implements it.