Define abstract interface for Agent / Peerboard

[FreeYourSoul]

Is your feature request related to a problem? Please describe. Interface should be able to :

• Register capability
• Request [[ arg: type capability -- intention ]]
• Retrieve Currently Required Capability (capability requested that doesn't exists)

[H4E]

First thing is : How Agent communicate with PeerBoard.

[H4E]

concept policy_comunication = ...

auto agent = std::make_unique<Agent>(fabko::policy_comunication);
peerboardId = registerPeerBoard("My board");  /* Not done if an Agent is not a server node */ 
peerboardId = Agent.connect ("My board");     /* Can also be found on P2P network amd return a virtual board etc... */
agent.query (peerboardId, query);  
agent.add (peerboardId, capability );
agent.subscribe (peerboardId, capability, callback);

[FreeYourSoul]

auto agent = std::make_unique<Agent>(fabko::policy_comunication);
peerboardId = registerPeerBoard("My board");  /* Not done if an Agent is not a server node */ 
handler_connection = Agent.connect ("My board");     /* Can also be found on P2P network etc... */
agent.query (query);   // query all known peerboard
handler_connection.query(query); // query secific peerboard
handler_connection.add (capability ); // specific peeboard
handler_connection.subscribe (capability, callback); // do it on a specific peeboard
agent.subscribe (capability, callback); // do it on all known peerboard