4.0.1

• Fix GraphQLRequest serialization with null input #412 #413
• Consider a case when both Optional & apiReturnType is used #410 #414
• Consider primitive types in ParametrizedInput classes #421 #423
• Scala: Refactor toString() and equals(), add examples #406 #411
• Scala: Optimizations and reformatting of generated classes #416 #417
• Refactor the library for multi-language support #407 #418
• Bump jackson-databind from 2.11.3 to 2.12.0 #409