Save the original recipient(s) in a question

### Pitch

Add the recipient id(s) into the question model, so there always is a reference to whom this question was initially sent to.

### Motivation

A question technically only has an author at the moment. If it is never answered and no inbox entries exist, we don't know where it was supposed to go to. 

This is a problem in terms of moderation, because we are losing a lot of context.