Code complexity: `update_keys()` in `solr/update_work.py` is too complex

[cclauss]

A continuation of #7883

The update_keys() async function in openlibrary/solr/update_work.py is 145+ lines long and is too complex... https://github.com/internetarchive/openlibrary/blob/112b89b2b5a37262664cd0f7647939a670e04833/openlibrary/solr/update_work.py#L1382-L1528

openlibrary/solr/update_work.py:1382:11: C901 `update_keys` is too complex (31 > 28)
openlibrary/solr/update_work.py:1382:11: PLR0912 Too many branches (24 > 22)
openlibrary/solr/update_work.py:1382:11: PLR0915 Too many statements (83 > 70)

Tasks:

• [ ] In a separate pull request, add a lot of tests for this function without modifying the function.
• [ ] After the first pull request has been merged, in a separate pull request:
  • [ ] In pyproject.toml remove this line "openlibrary/solr/update_work.py" = ["C901", "E722", "PLR0912", "PLR0915"]
  • [ ] Modify the update_keys() function so that it passes the tests created in step 1 as well as all ruff tests.

[scottbarnes]

In case it's any help, here's the current state of test coverage for update_keys(), where the red lines are not executed. Rather than despairing, I am interpreting this to mean there's lots of opportunity to write great new tests.