Add Case filtering per Business Unit (BU) for Admin Staffer roles

[baddlan]

In the listing view of Cases Staffers should have a dropdown of BUs they are members of so they can filter Cases by BU.

The request GET {{identities}}{{environment}}/staffs/id you will return the Staffer's BUs list among other info.

Cases can be filtered by BU as follows: GET {{cases}}{{environment}}/cases?owner=[BUs-UUID]