Support for PostgreSQL Arrays is missing for Value Relation multiple selection

[SrNetoChan]

Using a Value Relation Widget with the option Allow multiple selections works both in QGIS Desktop and Mergin maps app, in a PostgreSQL table as long as the field type is a varchar with enough size for storing a list of values separated by commas.

On the other hand, QGIS Desktop also works fine if the field column is an array of values, like a _varchar.

Mergin maps app doesn't seem to be ready for it yet. Although it looks good in the interface, showing all possible values and even showing previous selections, once you modify a value and save it, the database "stores" a NULL value instead of the selected values.

On PostgreSQL side, having an array allows better management of the list of values, powered by a good set of functions, so I think it would be interesting to be supported also by mergin maps.

Thanks for all your work!

[tomasMizera]

Thanks for the detailed description @SrNetoChan