error messages modified (https://github.com/gbif/registry/issues/565)

registry-security/src/main/java/org/gbif/registry/security/grscicoll/GrSciCollAuthorizationService.java

@@ -259,7 +259,7 @@ public EntityOperationResponse allowedToCreateInstitution(
       return new EntityOperationResponse(true);
     } else {
       return new EntityOperationResponse(
-          false, "Not allowed to create institutions for the country: " + country);
+          false, "Not allowed to create institutions for the country: " + (country == null ? "empty (Please provide a country with one of the addresses.)" : country));
     }
   }
 
@@ -287,9 +287,9 @@ public EntityOperationResponse allowedToCreateCollection(
       return new EntityOperationResponse(
           false,
           "Not allowed to create collections under the institution: "
-              + institutionKey
+              + (institutionKey == null ? "empty" : institutionKey)
               + " or in the country: "
-              + country);
+              + (country == null ? "empty (Please provide a country with one of the addresses.)" : country));
     }
   }
 

registry-security/src/test/java/org/gbif/registry/security/grscicoll/GrSciCollEditorAuthorizationFilterTest.java

@@ -414,6 +414,21 @@ public void collectionCreationAsMediatorAndCountryRightsTest() throws JsonProces
     assertDoesNotThrow(() -> filter.doFilter(mockRequest, mockResponse, mockFilterChain));
   }
 
+  @Test
+  public void collectionCreationAsMediatorTest() throws JsonProcessingException {
+    // GIVEN
+    mockCollectionCreation(ROLES_GRSCICOLL_MEDIATOR_ONLY, false, false);
+
+    // WHEN
+    WebApplicationException ex =
+      assertThrows(
+        WebApplicationException.class,
+        () -> filter.doFilter(mockRequest, mockResponse, mockFilterChain));
+
+    // THEN
+    assertEquals(HttpStatus.FORBIDDEN.value(), ex.getStatus());
+  }
+
   @Test
   public void institutionUpdateAsEditorWithEntityRightsTest() throws JsonProcessingException {
     // GIVEN