Fix implementation of AR-Identifier-2 (NOJIRA)

app/src/Model/Table/IdentifiersTable.php

@@ -288,6 +288,7 @@ public function ruleUniqueIdentifier($entity, $options) {
         // Note we specifically do NOT check status, since a Suspended Identifier
         // will still prevent duplicate assignment. (AR-Identifier-3)
         $whereClause = [
+          // type_id will imply CO ID, so we don't need to check it explicitly
           'type_id'     => $entity->type_id
         ];
 
@@ -297,6 +298,13 @@ public function ruleUniqueIdentifier($entity, $options) {
           $whereClause['identifier'] = $entity->identifier;
         }
 
+        // We need to only check Identifiers attached to the same type of Entity
+        if(!empty($entity->person_id)) {
+          $whereClause[] = 'person_id IS NOT NULL';
+        } elseif(!empty($entity->group_id)) {
+          $whereClause[] = 'group_id IS NOT NULL';
+        }
+
         $identifier = $this->find()
                            ->where($whereClause)
                            ->epilog('FOR UPDATE')