Verifies service exists before attaching permission.
Response built manually because calculated properties are not handled by .__dict()__
Request model uses Service ID mixin.
Service ID mixin verifies ID > 0
Org endpoints use query/body model dependencies to perform initial db lookups.
Issue #6
Org ID path params have been replaced with either query params (get endpoints) or body values.
Resolves#10
Endpoints in other modules that rely on an org model lookup have also been updated.
