Detect risky edxapp code changes

[robrap]

This could be discovery or just notes in a doc about future possibilities.

1. There have been ideas about detecting all migrations, or targeting risky migrations, etc.
   a. A risky migration might be one that touches any of our large tables, or makes certain types of changes.
   b. For blue/green code/migration changes, can we detect when changes are made in a single deployment that should be across deployments?
2. Could we detect new toggles to ensure we want the default value? We had an incident where we didn't want the default, but it is what we got.