This enables accessing the Extensions field, as defined in the response
format: https://spec.graphql.org/October2021/#sec-Response-Format
Extensions can be enabled using configuration option use_extensions.
This will change the return parameters of the generated client
functions. Making it a breaking change if enabled.
Since extensions are untyped as defined in the spec, the Client will
return an interface of type map[string]interface{}.
Jan-Hendrik Boll
b2422452a1