Joining from a database table to an action result and/or expanded filtering/aggregated when joining via action relationship

Currently, we can only link actions to database entities via action relationships. However, this functionality is extremely limited. There is no ability to filter out results or iterate. It would also be nice to be able to join from a table to an action result so you can get a superset of the table entity against the action dataset when the action is of type query.

No files, tests, or entry points are named. Start by locating the implementation of action relationships and query actions, then determine how table-to-action joins and filtering or aggregation are currently represented. Done should be defined by agreed behavior and coverage for the requested join and filtering scenarios.

Written by the indexing model from the issue text.