Initialize arrays of errors / error messages + minor refactoring (#1701)

* init error arrays correctly
* avoid nilPointer when syncing connectionPooler
* getInfrastructureRoles should return error
* fix unit tests and return type for getInfrastructureRoles

pkg/util/users/users.go

@@ -101,7 +101,7 @@ func (strategy DefaultUserSyncStrategy) ProduceSyncRequests(dbUsers spec.PgUserM
 // ExecuteSyncRequests makes actual database changes from the requests passed in its arguments.
 func (strategy DefaultUserSyncStrategy) ExecuteSyncRequests(requests []spec.PgSyncUserRequest, db *sql.DB) error {
 	var reqretries []spec.PgSyncUserRequest
-	var errors []string
+	errors := make([]string, 0)
 	for _, request := range requests {
 		switch request.Kind {
 		case spec.PGSyncUserAdd:
@@ -138,7 +138,7 @@ func (strategy DefaultUserSyncStrategy) ExecuteSyncRequests(requests []spec.PgSy
 				return err
 			}
 		} else {
-			return fmt.Errorf("could not execute sync requests for users: %v", errors)
+			return fmt.Errorf("could not execute sync requests for users: %v", strings.Join(errors, `', '`))
 		}
 	}