Ensures cross-DB compatibility for all types of both custom and user
profile fields, specifically when they're filtered and/or aggregated.
Implement stress testing of both via appropriate report sources.
Entities are re-usable collections of report columns and filters. When
creating system reports, we can re-use those elements from entities
without having to know specific details about their implementation.
They can be joined to reports, or other entities, using standard SQL
query syntax.
Define base classes, and create two example entities: course and user.
Co-Authored-By: David Matamoros <davidmc@moodle.com>
Paul Holden