To define custom @mention for certain team members similar to @here & @team

This feature will be very handy whenever you want to mention few members (of same role) in a private team chat or an open forum. This will stop bothering all team members @team or active team members @here who dont need any attention atm. Two instances of @mention for private team and global forum will be an additional benefit.

 Example below:

1. Private Team: "@designerteam can you fix this design issue" 

2. For global Forum: "@designerglobal we have a designers meet at this location"