Write a message

[iuresti]

As a user of teckers app (any role) I'm able to send messages to other users.

Acceptance criteria:

1. A message can be written by:
2. Clicking on the plus button on home/inbox screen
3. Clicking on the reply button on a message being displayed
4. A new screen should be opened to send the message. The screen must contain:
5. "Receiver(s)" (check the rules below)
6. Space to write the message
7. Icon to attach files/images
8. Icon to insert links
9. Button to cancel the message
10. Button to send the message
11. Space to write a subject
12. If the cancel button is clicked and a message has been written, a warning must be displayed to the user to indicate that everything will be lost if the dialog is closed
13. If the send button is clicked the message will be sent to all the receivers.

Rules for choose receivers:

1. Parent can only send a message to administrators
2. Tecker can only send a message to own mentors, team mates, administrators
3. Staff can only send a message to mentors and administrators
4. Mentors and administrators can send a message to anybody