The column type determines the available aggregation options present
for the column. Custom fields of type "select" should be considered as
text fields for this purpose, because their stored value represents
the index to their available options, rather than having any distinct
meaning of it's own for display.
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