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PostGraphile version: 4.4.4

postgraphile should honor variables in query string as defined in https://github.com/graphql/express-graphql#http-usage when the query is provided as post body.

with the following example request postgraphile does not honor the variables in the query string:

curl -XPOST 'localhost:5000/graphql?variables={"id":1}' -H 'content-type: application/graphql'  -d '
query MyQuery($id: Int) {
  something(id:$id) {
    name
  }
}
'

it would be nice if postgraphile could do this out of the box in order to support static query bodies from the client.