Quasi-quotation syntax for embedding GraphQL in Prolog text.
Prolog variables can be incorporated in the quasi-quotation using
the special lexical construct "<VarName>" where VarName is the name
of a variable that is an element of Args. See also option
variable_names(+VarNames) in graphql_read_document/3.
Result is a term representing the given GraphQL document in the
same format as used by graphql_read_document/3.