Direct message system

As a user I want to be able to send a message to just one person or a small group of selected people.
Similar to how DM's works in Linkedin or Facebook simplified (except we dont expect to be video or audio calls) 

**Mockups:**
(draft to give an idea)
https://www.figma.com/file/ww9GF90BJOJGKxlaYq3f8r/Upcoming-Features?node-id=19%3A17096