BUG: Dataspace configuration uses wrong dataspace for "Homepage layout" dropdown

[DennisClark]

Bug
When I create a new dataspace while signed in as a nexB reference data administrator, the form shows me a dropdown of the Card Layouts from the nexB dataspace on the "Homepage layout" field. Regardless of whether I choose one or not, this results in unwanted behavior in the new dataspace. When I sign in to the new dataspace, I see the Card Layouts defined for the nexB dataspace, which is not useful because the associated queries point to the wrong dataspace, and clicking on the "changelist" option cannot find the correct form. I can select a different card layout while signed in to the new dataspace, but that does not have an impact on the home page, which continues to present a dysfunctional nexB card layout.

To Reproduce
While signed in to nexB, open any non-nexB dataspace definition. You will see the the Card Layouts from the nexB dataspace on the "Homepage layout" field.

Expected behavior
Disable the "Homepage layout" field on the dataspace create/change form unless you are signed in to that dataspace. Do not assign or change the card layout on that dataspace.

Screenshots

[tdruez]

Context: The Dataspace and DejacodeUser models have special requirements due to their role in the system.

Dataspace is the root scoping model used as a reference for all other models. The scoping mechanisms don't apply to Dataspace itself.

The Dataspace.homepage_layout field is particularly tricky—it references a Dataspace-scoped model, but the Dataspace must exist before any value can be assigned to this field. Similarly, when creating a User, the Dataspace isn't assigned until after saving, so Dataspace-scoped data can't be displayed during creation.

To handle these constraints, the following changes were made in https://github.com/aboutcode-org/dejacode/pull/431/files:

• Added Dataspace FK validation on Dataspace and DejacodeUser models to prevent assigning objects from different Dataspaces
• Excluded the homepage_layout field from the Dataspace creation form (since the Dataspace doesn't exist yet)
• Made homepage_layout read-only on Dataspace and User change forms when the logged-in user is viewing a different Dataspace

In short: To manage homepage_layout, you must be logged into the same Dataspace as the object you're editing.