WIP trying to write a custom widget for relations

[jarofgreen]

No description provided.

[jarofgreen]

Many issues have come up with the many-to-many widget QGIS provides (and also we wanted a simpler UI here), and we looked into replacing it with a custom widget.

This branch represents the furthest I got with working on this. It contains much code from CoPilot.

It created a ofdsqgisplugin/widget_multiple_codelist.py file which looks hopefull, and on reading seems to have the various operations of selecting a current item or adding a new item (we can remove the deleting items stuff tho as we don't need this).

Where I ran into problems was then hooking this into QGIS. CoPilot at first tried to attach it to a existing field on the primary layer - but for a many to many link there is no field on the primary layer. After much re-prompting it started supplying code it said would set up a custom relation widget but it didn't work.

The problem is

relation_editor = QgsAttributeEditorElement.create(...)

This returns None with no error message and I couldn't work out why. I did find something suggesting that the tag and type for the dom variable where important, but I tried a whole range (you can see this in the PR) and nothing worked.

At this point I ran out of time to finish this.