feat: Filter user listing by type

[mashawes]

Wires the type query parameter into user listing so callers can filter by local, federated, and nonlocal users.

The provider and driver already supported this: UserListParameters carries a user_type field, the SQL driver's list filters local/nonlocal/federated accordingly, and it has unit tests. What was missing was the API layer, nothing read the query parameter or passed it down.

• Adds a UserType enum and a user_type field (deserialized from the type query key) to the api-types UserListParameters, and maps it through to the provider type in the conversion. Because the v4 user listing re-uses the same api-types parameters and conversion, ?type= now works on both the v3 and v4 user list endpoints.
• Adds API tests for ?type=local on both v3 and v4 confirming the filter reaches the provider.

Closes #234

Note: this contribution was developed with AI assistance.

[gtema]

Associated issue lists this, but maybe not very precise: this must be done for the api v4 only without touching v3. We can't introduce this new parameter into v3 since python keystone do not support it