- Add `created` and `modified` fields to `RenderedContent` models
- Add caching and RenderedContent docs
- Change cache key for library description rendered content
- Add `CLEAR_STATIC_CONTENT_CACHE_DAYS` setting
- Add manager method and task to clear static content cache
- Move task scheduler to main app
- Add daily task to clear rendered content cache
- Use created date and not updated date
- Add RenderedContent model and related helper methods
- Change StaticContentView `get()` logic to try the cache, then the db, then S3
- Change StaticContentView to update db appropriately
- Refactoring for readability/maintainability
