The endpoint configuration contains all the information needed during the handshake process
for this end point. All endpoints specify, for example, a URI. In the case of a server endpoint,
the URI signifies the URI to which the endpoint will be mapped. In the case of a client application
the URI signifies the URI of the server to which the client endpoint will attempt to connect.
Return the Decoder implementation classes configured. These
will be instantiated by the container to decode incoming messages
into the expected custom objects on MessageHandler.Whole.onMessage(Object)
the decoder implementation classes, the empty list if none.
This method returns a modifiable Map that the developer may use to store application
specific information relating to the endpoint that uses this
configuration instance. Web socket applications running on distributed
implementations of the web container should make any application
specific objects stored here java.io.Serializable, or the object may
not be recreated after a failover.