Factory that defines WebSocket extension. The factory is used in pair with WebSocketExtensionsConfig.install method to install WebSocket extension in client or server.
Usually this interface implemented in
companion object of the origin WebSocketExtension.
Create extension instance using config block. The extension instance is created for each WebSocket request.
Key is used to locate extension.
First extension bit used by current extension.
Second extension bit used by current extension.
Third extension bit used by current extension.