Enable assigning non-custom and custom stakeholders in registration

This update improves how organizations manage stakeholder involvement when new models are added to the model inventory during the registration process.

Administrators now have greater control over stakeholder setup. They can decide whether certain roles, such as “Model Owner”, are optional or required during model registration. This ensures that critical responsibilities are always assigned. The model creation form has also been redesigned to make stakeholder selection more straightforward. Roles are presented in a clear order, and users can be assigned to multiple roles, making the process more intuitive and less error-prone.

Finally, organization settings now offer a simpler way to manage role requirements. Administrators can configure these directly through the interface, making it easier to keep the system aligned with governance policies and organizational needs.