Context for a subscription operation, carrying either an HTTP request context or a WebSocket connection info.
The SSE path supplies requestContext; the WS path supplies
connection. Using this type (instead of IRequestContext)
prevents the WS path from silently handing resolvers an empty context.
The HTTP request context (supplied by the SSE path).
readonly
optional
connection: GraphqlConnectionInfo
The WebSocket connection info (supplied by the WS path).