[message_endpoint] sketch the structure

[zeroFruit]

message_endpoint name is referenced from: https://english.stackexchange.com/questions/369828/what-is-the-generic-term-for-sender-and-receiver
select endpoint to represent both sender and receiver.

MessageEndpoint basically do receiving packet and determine which logic executed based on the packet. Additionally MessageEndpoint call MemberDelgator to update member status, and encrypt data