ui: opt-in alert for link previews (#6799)

* ios: opt-in alert for link previews

* rename back

* kotlin: opt-in alert for link previews

* reset hints, refactor

* refactor hints

* move functions

* better UX

* ios buttons

* ios: two buttons

* kotlin refactor

* kotlin: two buttons

* show spinner only after preview decision

---------

Co-authored-by: Evgeny @ SimpleX Chat <259188159+evgeny-simplex@users.noreply.github.com>

apps/ios/Shared/Views/UserSettings/DeveloperView.swift

@@ -91,6 +91,11 @@ struct DeveloperView: View {
                 UserDefaults.standard.set(val, forKey: def)
             }
         }
+        for def in hintGroupDefaults {
+            if let val = groupAppDefaults[def] as? Bool {
+                groupDefaults.set(val, forKey: def)
+            }
+        }
         hintsUnchanged = true
     }
 }
@@ -98,6 +103,8 @@ struct DeveloperView: View {
 private func hintDefaultsUnchanged() -> Bool {
     hintDefaults.allSatisfy { def in
         appDefaults[def] as? Bool == UserDefaults.standard.bool(forKey: def)
+    } && hintGroupDefaults.allSatisfy { def in
+        groupAppDefaults[def] as? Bool == groupDefaults.bool(forKey: def)
     }
 }