add disable customer function

lib/pages/customer/model/customer_model.dart

@@ -95,4 +95,8 @@ class CustomerModel extends BaseModel {
     var snap = await Firestore.instance.collection(path).document(id).get();
     return User.fromMap(snap.data, snap.documentID);
   }
+
+  Future<void> enableUser(User user, bool enabled) {
+    return Services.instance.userService.enableUser(user.id, enabled);
+  }
 }