Ask before deleting operation

app/src/main/java/eu/faircode/email/FragmentOperations.java

@@ -20,6 +20,7 @@ package eu.faircode.email;
 */
 
 import android.content.Context;
+import android.content.DialogInterface;
 import android.content.Intent;
 import android.content.pm.PackageManager;
 import android.net.Uri;
@@ -130,6 +131,11 @@ public class FragmentOperations extends FragmentEx {
     }
 
     private void onMenuDelete() {
+        new DialogBuilderLifecycle(getContext(), getViewLifecycleOwner())
+                .setMessage(R.string.title_delete_operation)
+                .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
+                    @Override
+                    public void onClick(DialogInterface dialog, int which) {
                         new SimpleTask<Void>() {
                             @Override
                             protected Void onLoad(Context context, Bundle args) {
@@ -142,7 +148,11 @@ public class FragmentOperations extends FragmentEx {
                                 }
                                 return null;
                             }
-        }.load(this, new Bundle());
+                        }.load(FragmentOperations.this, new Bundle());
+                    }
+                })
+                .setNegativeButton(android.R.string.cancel, null)
+                .show();
     }
 
     private Intent getFAQIntent() {