fix: add missing unique key

Author: kenjis

src/Database/Migrations/2020-12-28-223112_create_auth_tables.php

@@ -46,6 +46,7 @@ public function up(): void
             'updated_at'   => ['type' => 'datetime', 'null' => true],
         ]);
         $this->forge->addPrimaryKey('id');
+        $this->forge->addUniqueKey(['type', 'secret']);
         $this->forge->addKey('user_id');
         $this->forge->addForeignKey('user_id', 'users', 'id', '', 'CASCADE');
         $this->forge->createTable('auth_identities', true);