Support GraphQL websocket authentication via connection_init message

[milgner]

While one can currently set HTTP headers for authentication, some GraphQL servers expect authentication information for subscriptions to be part of the connection_init message.

Conceptually I think that this is correct, too: the websocket logic should be able to stand on its own and not be tied to the surrounding HTTP transport.

It would be great if Insomnia would support adding authentication information to connection_init instead of HTTP headers, too.

Similar discussion at Postman: postmanlabs/postman-app-support#13278 - from the comment I gather that Altair does support this feature, I haven't tried it yet, though.