Function persisted_query 

pub fn persisted_query(request: &Request) -> bool

Whether the request is an Apollo persisted-query handshake.

A client with automatic persisted queries sends the hash alone, and sends the document only when the server says it has not seen that hash. Neither server implements the protocol; the difference is that Hasura says so – PersistedQueryNotSupported – and this used to run whatever document was beside the hash, which is the answer that looks like the handshake worked. A client would then send hash-only requests and get nothing back.