Policy change history outside of git

Why are we doing this work

Currently, we don't persist policy change history outside of git. This brings a number of limitations such as:

• inability to avoid race conditions when background jobs only get passed a policy ID, because the policy identified by the ID may have been mutated while the background job was queued
• inability to reliably determine the most recent policy editor, because a new commit may have been pushed while a background job remained queued, and there is no mapping from a policy's checksum to a git commit

Relevant links

• !208969 (comment 2832445280)
• #563867 (comment 2826712933)

Non-functional requirements

• Documentation:
• Feature flag:
• Performance:
• Testing:

Implementation plan

TBD

Verification steps

TBD