Request: Implement "Private Chat" functionality

[Knezzen]

Hi!

Thanks again for an awesome client for macOS!

While writing with a regular on System 7 Today yesterday I noticed that what appears to be a private chat on "new" Hotline actually uses the "Private Message" function which more or less floods the older clients with new windows for every message received. It's hard to keep track of a typical chat communication while using the classic Hotline clients, and I feel like the interface in "new" Hotline is more representative of how the "Private Chat" (since Hotline 1.8.x?) function works.

Would it be possible to implement the current "Private Message" functionality in a more email or "one shot message" type of fashion and make the current private chat function (clicking on a user in the userlist to chat in private) use the "Private Chat" functionality in the Hotline protocol instead?

Thanks so much for your hard work! It really gives the Hotline community a new breath of life :)