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

Reviewed-on: #64

lib/models/requests/set_state.dart

@@ -1,22 +1,23 @@
 import "package:freezed_annotation/freezed_annotation.dart";
 import "package:nexus/models/content/content.dart";
 import "package:nexus/models/ms_duration.dart";
+
 part "set_state.freezed.dart";
 part "set_state.g.dart";
 
-@freezed
-abstract class SetStateRequest with _$SetStateRequest {
-  const factory SetStateRequest({
-    required String roomId,
-    required String type,
-    required String stateKey,
-    required Content content,
+@Freezed(toJson: false, fromJson: false)
+@JsonSerializable()
+class const SetStateRequest({
+  required final String roomId,
+  required final String type,
+  required final String stateKey,
+  required final Content content,
 
-    @JsonKey(name: "delay_ms", includeIfNull: false)
-    @MSDuration()
-    @Default(null)
-    Duration? delay,
-  }) = _SetStateRequest;
+  @JsonKey(name: "delay_ms", includeIfNull: false)
+  @MSDuration()
+  final Duration? delay,
+}) with _$SetStateRequest {
+  Map<String, Object?> toJson() => _$SetStateRequestToJson(this);
 
   factory SetStateRequest.fromJson(Map<String, Object?> json) =>
       _$SetStateRequestFromJson(json);