Improves the existing document rejection process by actually marking a
document as completed cancelling further actions.
## Related Issue
N/A
## Changes Made
- Added a new rejection status for documents
- Updated a million areas that check for document completion
- Updated email sending, so rejection is confirmed for the rejecting
recipient while other recipients are notified that the document is now
cancelled.
## Testing Performed
- Ran the testing suite to ensure there are no regressions.
- Performed manual testing of current core flows.
Introduces the ability for users with the **Assistant** role to prefill
fields on behalf of other signers. Assistants can fill in various field
types such as text, checkboxes, dates, and more, streamlining the
document preparation process before it reaches the final signers.
