ETA: September 1, 6 PM
Availability: Mon-Fri 10AM-15PM

Most xref tables can created automatically by Django, so this issue needs to be rewritten to define the many to many relationship.

After slack messaging with @del9ra, we realized that probably none of the xref tables can use the "through" table generated by Django, because the generated table won't contain the created_at and updated_at fields defined in the abstract base class. So in that case, we should discuss @del9ra's suggestion to create another abstract base class to add a standardized ended_at field to all the xref table models that inherit from it.

In any case, that means this issue does still need to implement a new model.

After slack messaging with @del9ra, we realized that probably none of the xref tables can use the "through" table generated by Django, because the generated table won't contain the created_at and updated_at fields defined in the abstract base class. So in that case, we should discuss @del9ra's suggestion to create another abstract base class to add a standardized ended_at field to all the xref table models that inherit from it.

Variations of ended are used not only in xref models but also in other models: ended_at in the Affiliation model, ended in the Permission model, project_sponsor_partner_xref, and permission_history, and ended_on in project_language_xref and project_sdg_xref.

In any case, that means this issue does still need to implement a new model.

@fyliu I didn't implement a new model in my new PR #398 ; I just added a program_areas many-to-many field in the Project model.

I think we need to discuss with @Neecolaa on using the same name and type for the xref table to mark when the relationship ended. Adding "ready for DB Architect" and will add an item to the next meeting.

@del9ra I think we do need to add the xref model just because the created timestamp is a requirement and that model would provide it. I would wait for @dmartin4820's PR #385 to be merged and use that as a model for this issue.

@fyliu #376 (comment) Here you said:

"...this xref table doesn't have any extra data fields other than the relations (foreign keys). It means that we don't really need to create a Django model for this table at all.."