Add Currency default value handling

[nithy1603]

Please add feature to handle default values for Currency in GraphQL Schema.

Description:

We have defined a custom scalar for currency extending graphql-java-extended-scalars Currency scalar. A typemapping for the custom scalar is provided for the graphqlcodegen-maven-plugin as follows

java.util.Currency

An input type MoneyInput is defined in the graphql schema with a default value for currency
input MoneyInput {

currency: CustomCurrency! = "USD"

value: Decimal!

}

The compilation give the following error:
incompatible types: java.lang.String cannot be converted to java.util.Currency

[srinivasankavitha]

Thanks for creating this issue. Will fix in the next release.