Version/2.10.3 (#597)

* Fixed #553 Generation putIfAbsent for names begins with "Map"

* Removed not needed property

* Removed toJson generation

* Returned generation of toJson()

* Implemented toJson only for some models feature

* Fixed some errors

* Added some fixes

* Added createToJson: false for models without toJson

* Fixed #554 generation of putIfAbsent for not needed schemas

* Updated pubspec and changelog

* Reverted change in analysis_options

* Fixed warnings

* Fixed generation of multipart data

* Fixed parameter type generation

* Changed dynamic to Object

* Some fixes

* Add recognition of int64 as int

* Fixed #571

* Fixed #572

* Fixed #570

* Fix #576

* Updated changelog

* Some fixed in configs

* Reverted changes

* implemented support of multipart for border cases

* Added fix for partFile parameters

* Updated pubspec and changelog

* Formatted lib folder

* Fixed warning

* Updated libs
Fixed generation of with base url

* Small fix

* Fixed dependencies

* Added support of nullabe responses

---------

Co-authored-by: Uladzimir Paliukhovich <uladzimir_paliukhovich@epam.com>

lib/src/code_generators/swagger_requests_generator.dart

@@ -1075,8 +1075,12 @@ class SwaggerRequestsGenerator extends SwaggerGeneratorBase {
         return kObject.pascalCase;
       }
 
-      final typeName =
+      var typeName =
           getValidatedClassName(schemaRef.getRef()).withPostfix(modelPostfix);
+
+      if(neededSchema.isNullable) {
+        typeName = typeName.makeNullable();
+      }
 
       return typeName;
     }