feat: update AuthModel serialization to use explicitToJson for nested objects

packages/apidash_core/lib/models/auth/api_auth_model.dart

@@ -10,6 +10,7 @@ part 'api_auth_model.freezed.dart';
 
 @freezed
 class AuthModel with _$AuthModel {
+  @JsonSerializable(explicitToJson: true)
   const factory AuthModel({
     required APIAuthType type,
     AuthApiKeyModel? apikey,

packages/apidash_core/lib/models/auth/api_auth_model.freezed.dart

@@ -226,7 +226,8 @@ class __$$AuthModelImplCopyWithImpl<$Res>
 }
 
 /// @nodoc
-@JsonSerializable()
+
+@JsonSerializable(explicitToJson: true)
 class _$AuthModelImpl implements _AuthModel {
   const _$AuthModelImpl(
       {required this.type, this.apikey, this.bearer, this.basic, this.jwt});

packages/apidash_core/lib/models/auth/api_auth_model.g.dart

@@ -26,10 +26,10 @@ _$AuthModelImpl _$$AuthModelImplFromJson(Map<String, dynamic> json) =>
 Map<String, dynamic> _$$AuthModelImplToJson(_$AuthModelImpl instance) =>
     <String, dynamic>{
       'type': _$APIAuthTypeEnumMap[instance.type]!,
-      'apikey': instance.apikey,
-      'bearer': instance.bearer,
-      'basic': instance.basic,
-      'jwt': instance.jwt,
+      'apikey': instance.apikey?.toJson(),
+      'bearer': instance.bearer?.toJson(),
+      'basic': instance.basic?.toJson(),
+      'jwt': instance.jwt?.toJson(),
     };
 
 const _$APIAuthTypeEnumMap = {