allow Coercing.parseLiteral to return null (remove @NonNull annotation) #2904
Description
Coercing.parseLiteral is declared to return a @NonNull value.
However, a coercing may want to return null for the NullValue. See for example the ObjectScalar implementation in https://github.com/graphql-java/graphql-java-extended-scalars