Make factories for snippets, other models

We have snippets and other models that need factories written for good tests ( this can include permissions, for example). If we write these factories too we'll be in much better shape to support programmatic testing and avoid setting up fixtures or tests using the database.

No files, tests, or entry points are named. Start by locating the snippets and other model definitions, then identify the existing factory and fixture patterns. Done means factories cover the needed models and permissions so tests can use them without manual fixtures or database setup.

Written by the indexing model from the issue text.