NIOTypedWebSocketServerUpgrader

Users may frequently want to offer multiple websocket endpoints on the same port. For this reason, this WebServerSocketUpgrader only knows how to do the required parts of the upgrade and to complete the handshake. Users are expected to provide a callback that examines the HTTP headers (including the path) and determines whether this is a websocket upgrade request that is acceptable to them.

This upgrader assumes that the HTTPServerUpgradeHandler will appropriately mutate the pipeline to remove the HTTP ChannelHandlers.