restore: skipDnsSetup flag

src/restore.html

@@ -212,9 +212,18 @@
                                     <input type="text" class="form-control" ng-model="password" id="inputConfigureBackupPassword" name="prefix" ng-disabled="busy" placeholder="Passphrase used to encrypt the backups" ng-required="encrypted">
                                 </div>
 
+                                <div class="checkbox">
+                                    <label>
+                                        <input type="checkbox" ng-model="skipDnsSetup"><b>Dry run</b> <sup><a ng-href="https://docs.cloudron.io/backups/#restore-cloudron-dry-run" class="help" target="_blank"><i class="fa fa-question-circle"></i></a></sup>
+                                    </label>
+                                    <br/>
+                                    <small>Use this option for testing your backups before migration. The DNS records are not updated and this browser's host must have an entry in <code>/etc/hosts</code> for the dashboard domain to this server's IP.</small>
+                                </div>
+
                                 <input class="ng-hide" type="submit" ng-disabled="configureBackupForm.$invalid"/>
 
                                 <div uib-collapse="!advancedVisible">
+
                                     <div class="form-group">
                                         <label class="control-label">IP Configuration  <sup><a ng-href="https://docs.cloudron.io/networking/#ip-configuration" class="help" target="_blank"><i class="fa fa-question-circle"></i></a></sup></label>
                                         <select class="form-control" ng-model="sysinfo.provider" ng-options="a.value as a.name for a in sysinfoProvider"></select>