Support robust initialisation of user controlled signing

[bjorntore]

Where can we run the nessecary initialisation logic for finding signees, delegating access rights and notifying them in a robust and safe manner.

Make Start-hook more robust? Automatic API-call from frontend?

Research and suggest solution.

For MVP we run the process Next until done, while keeping state in signeeState which will be reflected in SigneeList and CTA components. For API users, a call to signing/getState(s) in required to see state.

[bjorntore]

Parking for now. Revisiting later.

[cammiida]

All logic for initializing signees is done in the Start-hook of the signing task. There is not retry mechanism if anything fails. Make this more robust with the new process engine in v9.