Mentions should be case insensitive

I think there was another socra for this but couldn't find it. Should be able to mention a user, an

I think there was another socra for this but couldn't find it. Should be able to mention a user, and the mention should always be case insensitive. - [ ] make sure mention is created regardless of casing

**Summary:** There was mention of another SOCRA for this, but it could not be found. The ability to mention a user should always be case insensitive.