Add a better messaging interface for sellers

[omzlo]

Form discord:

• I've been in a conversation with multiple people (via the send message to customer function) and I am starting to loose track. It would be nice if there was a "message inteface" where I can see recent messages and sorted by date, in threads (by order) and indicating who sent last message. Something like a simple e-mail client.
• [...] there are several inconveniences with the current implementation, the most annoying for me is that when I start answer a message, previous message(s) is no longer visible. Due to the several inconveniences I often move dialogues to my email instead of using the Lectronz messaging system.

[danielkucera]

Would it be possible to configure a separate e-mail address for "Send a message to the seller" from within order function and generic "Message seller" so I can direct these two to an external ticketing system?

[arturo182]

Something like Hackaday's messaging interface would be great, but I do realize that it is a substantial amount of work