The model factories lived in the documents test package, but three other
apps needed them. The AI, mail and testing suites all reached across an app
boundary to import from documents.tests.factories, which made a private test
package into a shared dependency.
The factories now live in the shared testing package, where cross-app use is
the intended use.
* Feature: parse advanced search with whoosh-compat and delete the hand-written translator
* Don't cover these, they exist for defensive, but there's no other current diagnostic
* A mix of more no cover and tests
* Route SCHEMA_FIELD_MISSING into an error, not an HTTP 400
Trenton H