throw error when assigning role to a user who is not found in the aai registry

src/main/java/eu/dnetlib/repo/manager/service/security/AuthorizationServiceImpl.java

@@ -88,6 +88,9 @@ public class AuthorizationServiceImpl implements AuthorizationService {
             throw new ResourceNotFoundException("Cannot find CouId for role: " + role);
         }
         List<Integer> coPersonIds = aaiRegistryService.getCoPersonIdsByEmail(email);
+        if (coPersonIds.isEmpty()) {
+            throw new ResourceNotFoundException("User with email '%s' could not be found..");
+        }
         for (Integer coPersonId : coPersonIds) {
             assert coPersonId != null;
             aaiRegistryService.assignMemberRole(coPersonId, couId);