Assign opener or opener_file's to other users

[jeffe]

Is your feature request related to a problem? Please describe.
While interacting with the bot via mentions a custom opener can be set for the channel or yourself.

Describe the solution you'd like
To be able to assign a custom opener/opener_file to other users. Eg, @user1 should always be assigned to use tutor.json, @user2 should always be assigned to use engineer.json when mentioning the bot

Additional context
As a super-bonus awesome feature, it would be nice to be able to assign a model to the users opener