Support adding attachment to message

[JovicaSusa]

Part of: https://github.com/BookingSync/BookingSync-Core/issues/4305

We need to support adding attachments to message. We should use add_attachment endpoint in api v3 messages controller.

[thilonel]

Isn't flat a bit too low? That's for very simple stuff, this seems a bit more complex. Am I wrong?

[JovicaSusa]

Yeah, if flat is for very simple stuff then maybe tube is more appropriate. I'm still not sure with estimating, so flat would be something that's really quick, like some straightforward simple change?

[thilonel]

https://knowledgedatabase.happystay.com/en/tech-team-ticket-management ;)