allow manual admin filtering of anonymous messages

[nminchow]

@BIT in the discord proposed some kind of filtering step to moderate comments. It would probably need to relay messages to a given channel and wait for a reaction, and then send it through. Hopefully, we'd be able to store all of the information needed to send the message to the desired target in the "approval" form of the message.

The tricky part here may be identifiers. Worst case, we just bake that into the message that needs approval.