chore: Display story privacy warning

assets/l10n/intl_en.arb

@@ -2692,5 +2692,7 @@
   },
   "whoCanSeeMyStoriesDesc": "Please note that people can see and contact each other in your story.",
   "whatIsGoingOn": "What is going on?",
-  "addDescription": "Add description"
+  "addDescription": "Add description",
+  "storyPrivacyWarning": "Please note that people can see and contact each other in your story. Your stories will be visible for 24 hours but there is no guarantee that they will be deleted from all devices and servers.",
+  "iUnderstand": "Ich verstehe"
 }

lib/pages/add_story/invite_story_page.dart

@@ -2,6 +2,7 @@
 
 import 'package:flutter/material.dart';
 
+import 'package:adaptive_dialog/adaptive_dialog.dart';
 import 'package:flutter_gen/gen_l10n/l10n.dart';
 import 'package:future_loading_dialog/future_loading_dialog.dart';
 import 'package:matrix/matrix.dart';
@@ -27,6 +28,13 @@ class _InviteStoryPageState extends State<InviteStoryPage> {
   final Set<String> _invite = {};
 
   void _inviteAction() async {
+    final confirmed = await showOkCancelAlertDialog(
+      context: context,
+      message: L10n.of(context)!.storyPrivacyWarning,
+      okLabel: L10n.of(context)!.iUnderstand,
+      cancelLabel: L10n.of(context)!.cancel,
+    );
+    if (confirmed != OkCancelResult.ok) return;
     final result = await showFutureLoadingDialog(
       context: context,
       future: () async {
@@ -62,9 +70,6 @@ class _InviteStoryPageState extends State<InviteStoryPage> {
         .client
         .getUndecidedContactsForStories(widget.storiesRoom)
         .then((contacts) {
-      if (contacts.length < 20) {
-        _invite.addAll(contacts.map((u) => u.id));
-      }
       return contacts;
     });
     return Scaffold(