Admin: Cal-ITP Benefits staff user can add Claims models

[angela-tran]

This is for breaking up the part of #2638 that sets visible/nonvisible and editable/readonly permissions on the fields of ClaimsProvider for superuser and Cal-ITP group members, and lets Cal-ITP group members add instances of the ClaimsProvider model.

Acceptance Criteria

superuser

• Confirm all fields are visible and editable as before
• Confirm instances of ClaimsProvider can be added as before

Cal-ITP group member

• Confirm correct fields are visible/nonvisible, and editable/readonly
• Confirm new instances of the ClaimsProvider model can be added AND saved

[angela-tran]

Luis will fill out the acceptance criteria on this ticket.