bug: WebSocketGraphQLClient handshake fails if it receives a keep alive message before connection ack

[vincentjames501]

According to the spec, it doesn't really define what should happen if the client receives a message before the connection ack message.

Some GQL servers such as Hasura (see hasura/graphql-engine#7002) will send a "ka" message immediately upon a client connecting.

The dgs client is pretty strict when it comes to what the next message should be which one could argue is one interpretation of the spec.

    private fun doHandshake(): Mono<Void> {
        return Mono.defer {
            connection.set(client.connect().subscribe())

            client.send(CONNECTION_INIT_MESSAGE)
            client.receive()
                .take(1)
                .map { message ->
                    if (message.type == GQL_CONNECTION_ACK) {
                        message
                    } else {
                        throw GraphQLException("Acknowledgement expected from server, received $message")
                    }
                }
                .timeout(acknowledgementTimeout)
                .then()
        }
    }

Since this is an internal private function it's also quite hard to override.

Expected behavior

Ideally it would be nice to be able to just skip messages until we receive the GQL_CONNECTION_ACK or timeout while maybe logging messages skipped/dropped before then?

Actual behavior

It throws an exception and aborts the connection.

reactor.core.Exceptions$ErrorCallbackNotImplemented: graphql.GraphQLException: Acknowledgement expected from server, received OperationMessage(type=ka, payload=null, id=)
Caused by: graphql.GraphQLException: Acknowledgement expected from server, received OperationMessage(type=ka, payload=null, id=)
	at com.netflix.graphql.dgs.client.WebSocketGraphQLClient$doHandshake$1$1.invoke(WebSocketGraphQLClient.kt:138)
	at com.netflix.graphql.dgs.client.WebSocketGraphQLClient$doHandshake$1$1.invoke(WebSocketGraphQLClient.kt:134)
	at com.netflix.graphql.dgs.client.WebSocketGraphQLClient.doHandshake$lambda$7$lambda$6(WebSocketGraphQLClient.kt:134)

Steps to reproduce

Point an instance of the WebSocketGraphQLClient as any Hasura subscription which will fail.