feat: add new column 'identifier' to the Users table

Details:
- Added a new column named 'identifier' to the Users table.

backend/src/database/migrations/20240507184134-add-identifier-to-users.ts

@@ -0,0 +1,14 @@
+import { QueryInterface, DataTypes } from "sequelize";
+
+module.exports = {
+  up: (queryInterface: QueryInterface) => {
+    return queryInterface.addColumn("Users", "identifier", {
+      type: DataTypes.STRING,
+      allowNull: true
+    });
+  },
+
+  down: (queryInterface: QueryInterface) => {
+    return queryInterface.removeColumn("Users", "identifier");
+  }
+};

backend/src/models/User.ts

@@ -51,6 +51,9 @@ class User extends Model<User> {
   @Column
   transferToOtherQueues: boolean;
 
+  @Column
+  identifier: string;
+  
   @Default("admin")
   @Column
   profile: string;