backups: send chown flag for mountpoint

src/views/backups.html

@@ -205,6 +205,13 @@
             </label>
           </div>
 
+          <!-- mountpoint -->
+          <div class="checkbox" ng-show="configureBackup.provider === 'mountpoint'">
+            <label>
+              <input type="checkbox" ng-model="configureBackup.chown">{{ 'backups.configureBackupStorage.chown' | tr }}</input>
+            </label>
+          </div>
+
           <!-- S3/Minio/SOS/GCS/UpCloud -->
           <div class="form-group" ng-class="{ 'has-error': configureBackup.error.endpoint }" ng-show="configureBackup.provider === 'minio' || configureBackup.provider === 'upcloud-objectstorage' || configureBackup.provider === 'backblaze-b2' || configureBackup.provider === 's3-v4-compat'">
             <label class="control-label" for="inputConfigureBackupEndpoint">{{ 'backups.configureBackupStorage.s3Endpoint' | tr }}</label>