* chore: refactor user subject logic to be in 1 place
* test: implement test to assert deleted custom roles are omitted
* add unit test for deleted role
* chore: create type for unique role names
Using `string` was confusing when something should be combined with
org context, and when not to. Naming this new name, "RoleIdentifier"
Includes db schema and dbauthz layer for upserting custom roles. Unit test in `customroles_test.go` verify against escalating permissions through this feature.