Workflow overhaul

[jekabs-karklins]

Upcoming Workflow Engine Changes

We’re implementing four key improvements to make workflows more robust, flexible, and easier to maintain. Feedback is welcome.

1. Event Validity
   Events must now occur while the proposal is in the source state to trigger a transition.
   Prevents outdated events (e.g., PROPOSAL_UPDATED before entering state A) from causing unintended moves.

2. Conditions
   Transitions can now require state-based conditions in addition to events.
   Example: Event PROPOSAL_INSTRUMENT_ADDED + Condition PROPOSAL_HAS_INSTRUMENT = true.
   Allows finer control and avoids unnecessary transitions.

3. Circular Workflows
   We can now safely return to earlier states without infinite loops, thanks to event validity + conditions.
   Supports iterative review cycles without hacky detours.

4. Multiple States per Status ID
   Different workflow states can share the same statusId but have unique exit rules.
   Example: Two REJECTED states with different recovery paths.
   Enables richer branching and context-specific transitions.

Comments welcome, especially on backward-compatibility and circular workflow safeguards.