Multiple ConfigContext can be created with the same name

[glennmatthews]

Environment

• Python version: any
• Nautobot version: 1.0.1

Steps to Reproduce

1. Create a ConfigContext.
2. Create a second config context with the same name string.

Expected Behavior

Creation of the second same-named ConfigContext should fail or be blocked by the UI due to the duplicate name. This is the behavior shown in NetBox 2.10.x.

Observed Behavior

Multiple same-named config contexts can coexist. This is problematic because, in the case of multiple contexts having the same weight, ties are broken based on the context name.

This appears to be another case where a unique_together constraint is not working as one might expect due to NULL!=NULL behavior of the database, as ConfigContext defines unique_together = [["name", "owner_content_type", "owner_object_id"]] and in common usage owner_content_type and owner_object_id will be NULL values.