Allow pinning of Direct Message conversations

As a server owner, I receive numerous DMs from my members per day. Sometimes it's not the right time to respond but I have opened their message for whatever reason. This results in the conversation getting buried and forgotten. My proposed solution to this would be to allow us to pin conversations to the top of the Direct Messages list. This would allow us to prioritize our responses to users while not ignoring or forgetting to respond to someone, especially in the case where we may be waiting on a reply from them and then receive other conversations in the meantime.