refactor: Add schema validation to PH log metadata

[rgraber]

Checklist

1. If you've added code that should be tested, add tests
2. If you've changed APIs, update (or create!) the documentation
3. Ensure the tests pass
4. Run ./python-format.sh to make sure that your code lints and that you've followed our coding style
5. Write a title and, if necessary, a description of your work suitable for publishing in our release notes
6. Mention any related issues in this repository (as #ISSUE) and in other repositories (as kobotoolbox/other#ISSUE)
7. Open an issue in the docs if there are UI/UX changes
8. Create a testing plan for the reviewer and add it to the Testing section
9. Add frontend or backend tag and any other appropriate tags to this pull request

Description

Developer-facing changes only.

Notes

Add schema validation to make sure certain fields are in the project history log metadata. Eventually it should be filled out more detail for the different kinds of PH logs; this is just a start.

Testing

None needed. Refactor.

[notion-workspace]

Create project-history audit logs