Implemented room member and room info

In preperation for upcoming room screens.

RoomInfo is supposed to be used in conjunction with
the Room class.
They are not merged (Room as a attribut in RoomInfo),
because whilst Room can be stored on disk,
RoomInfo can not.
This is done to prevent tampering with the data
(when offline).

This also makes hiding elements easier when the user is offline,
as we can just pretend, that they do not have the required permission.

lib/backend/room.dart

@@ -262,4 +262,49 @@ class Room {
     final db = Localstore.instance;
     await db.collection('rooms').doc('$id@$serverTag').set(toMap());
   }
+
+  static Future<Room> fromDisk({required String id, required String serverTag}) async {
+    final db = Localstore.instance;
+    final raw = await db.collection('rooms').doc('$id@$serverTag').get();
+    return Room.fromMap(raw!);
+  }
+}
+
+class ShoppingListItem {
+
+}
+
+class RoomMember {
+  final String id;
+  final String serverTag;
+  final bool isAdmin;
+
+  const RoomMember(
+      {required this.id, required this.serverTag, required this.isAdmin});
+
+  factory RoomMember.fromJSON(dynamic json) {
+    return RoomMember(
+        id: json['name'], serverTag: json['server'], isAdmin: json['admin']);
+  }
+}
+
+class RoomInfo {
+  final String owner;
+  final bool isAdmin;
+  final bool isOwner;
+  final int permissions;
+
+  const RoomInfo(
+      {required this.permissions,
+      required this.owner,
+      required this.isAdmin,
+      required this.isOwner});
+
+  factory RoomInfo.fromJSON(dynamic json) {
+    return RoomInfo(
+        permissions: json['rights'],
+        owner: json['owner'],
+        isAdmin: json['isAdmin'],
+        isOwner: json['isOwner']);
+  }
 }