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

Reviewed-on: #64

lib/models/requests/set_membership.dart

@@ -1,18 +1,19 @@
 import "package:freezed_annotation/freezed_annotation.dart";
 import "package:nexus/models/membership_action.dart";
+
 part "set_membership.freezed.dart";
 part "set_membership.g.dart";
 
-@freezed
-abstract class SetMembershipRequest with _$SetMembershipRequest {
-  const factory SetMembershipRequest({
-    required String userId,
-    required String roomId,
-
-    String? reason,
-    @JsonKey(name: "action") required MembershipAction action,
-    @Default(false) @JsonKey(name: "msc4293_redact_events") bool redact,
-  }) = _SetMembershipRequest;
+@Freezed(toJson: false, fromJson: false)
+@JsonSerializable()
+class const SetMembershipRequest({
+  required final String userId,
+  required final String roomId,
+  final String? reason,
+  @JsonKey(name: "action") required final MembershipAction action,
+  @JsonKey(name: "msc4293_redact_events") final bool redact = false,
+}) with _$SetMembershipRequest {
+  Map<String, Object?> toJson() => _$SetMembershipRequestToJson(this);
 
   factory SetMembershipRequest.fromJson(Map<String, Object?> json) =>
       _$SetMembershipRequestFromJson(json);