ttyniwa

@andrey-ushakov Could you merge #62 & #63 and release?

I tested that this PR works on Android 8.

BTW, GraphQLQuery, Mutation, Subscription has default value as empty string. https://github.com/leangen/graphql-spqr/blob/master/src/main/java/io/leangen/graphql/annotations/GraphQLQuery.java#L17 I think it's better to make the same correction to GraphQLArgument for consistency.

Below code is a temporary resolution patch. This code affects not only graphql-spqr, but also your code. ``` import example.StringToMapConverter import org.springframework.context.annotation.Configuration import org.springframework.format.FormatterRegistry import org.springframework.web.servlet.config.annotation.WebMvcConfigurer @Configuration class WebMvcConfig :...