Batch change trigger for code monitoring

[eseliger]

Part of https://github.com/sourcegraph/sourcegraph/issues/31534

This ticket captures the engineering effort for a code monitoring -> batch changes integration. It is a collection of tasks, questions and engineering problems to solve.

All estimates are very rough guesses. The big unknown here is the code pattern for integrating two enterprise features. I have a couple of ideas how it could work, but we need to prove that it actually does. This will allow us to build cross feature integrations in the future so it is definitely not wasted effort, from a company perspective.

• Come up with code pattern for integrating two enterprise features #34648
  • Separate batchescodemonitors package?
• Implement link from BatchChange -> CodeMonitor (or [CodeMonitor!]?) 1d
• UI: Display when watched by a code monitor on BC page 1d
• Extract code from hackathon to add a new code monitor action type, add tests and polish it 3d
• Should there be a 1-1 connection between BC and CodeMonitor, or M-N?
• Implement auto-apply flag (partially done in prototype) 2d
  • What about concurrent executions? Should only the latest auto-apply?
  • tech debt: store layer reaching into service layer
• Implement auto execution flag (partially done in prototype) 2d
  • Improve code quality, surface errors, write tests
• Code monitor handleBatchChange trigger code (partially done in prototype) 2d
  • Under which user is the new execution created?
  • Add access enforcement
  • Add tests