Move to Flutter 3.47, use the improvements that come with this (#64)

Reviewed-on: #64

lib/models/configs/user.dart

@@ -1,11 +1,13 @@
 import "package:freezed_annotation/freezed_annotation.dart";
+
 part "user.freezed.dart";
 part "user.g.dart";
 
-@freezed
-abstract class UserConfig with _$UserConfig {
-  const factory UserConfig({required String? roomId, required String userId}) =
-      _UserConfig;
+@Freezed(toJson: false, fromJson: false)
+@JsonSerializable()
+class const UserConfig({final String? roomId, required final String userId})
+    with _$UserConfig {
+  Map<String, Object?> toJson() => _$UserConfigToJson(this);
 
   factory UserConfig.fromJson(Map<String, Object?> json) =>
       _$UserConfigFromJson(json);