STT-1031 create state change service and proposal submit endpoint
Per our post-stand-up conversation, this MR provides the state change service without the actual work of copying the author copy to observatory copy.
It does include:
- proposal validation service call
- it also includes the submission endpoint (which was in a previous separate closed MR)
**This MR should enable Reid to interact with the backend in a way that completes STT-1028 and STT-1030. **
The known state transition from Draft to Submitted is currently well-understood. Other state transition requests will result in a ValueError being returned.
If proposal validation fails for any reason, a ValueError is returned to the caller. I've added the need to surface all errors to the FE as an item in the gripes list.
Edited by Mark Ferguson