Architecture diagrams of HttpServer and Connection lifecycle (#148)

* add arch diagrams and menu

* fix colors for arch diagrams

* refine architecture diagrams, ready for review

* capitalize titles and add mmdc instruction

* apply code review requested changes

* Add links to accept, worker and dispatcher too

static/img/diagrams/connection_accept.mmd

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+sequenceDiagram
+
+participant ServerBuilder
+participant mio
+participant Accept
+participant WorkerClient
+
+
+ServerBuilder->>Accept: start(socks, workers)
+loop Continuous: poll
+	Accept->>mio: mio::Poll::poll()
+	alt poll() -> TIMER | CMD
+		Accept-->>Accept: process_*
+	else poll() -> NOTIFY
+		Accept->>Accept: backpressure
+	else poll() -> OTHER(token)
+		Accept-->>Accept: accept_one(Conn)
+		loop while exist WorkerClient
+			Accept->>WorkerClient: send(Conn)
+			alt send(Conn) -> Ok(_)
+				Note over Accept: break loop
+			else send(Conn) -> Err(_)
+				Accept->>ServerBuilder: worker_faulted(idx)
+				Accept->>Accept: remove worker, get next worker				
+			end
+		end
+	end
+end

static/img/diagrams/connection_overview.mmd

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+sequenceDiagram
+
+participant ServerBuilder
+participant Accept
+participant WorkerClient
+participant Worker
+participant Dispatcher
+
+ServerBuilder->>Accept: start(socks, workers)
+
+Note over Accept: accept Connections
+loop poll connections on sockets
+	activate Accept
+	Accept-->>Accept: poll() --> Conn
+	Note over Accept: backpressure logic
+	Accept->>WorkerClient: send(Conn)
+end
+deactivate Accept
+
+Note over Worker: process Connections
+loop Worker as Future::poll
+	activate Worker
+	Worker->>WorkerClient: rx.poll_next()
+	Note over Worker: Service factories
+	Worker-->>Dispatcher: new(stream)
+end
+deactivate Worker
+
+Note over Dispatcher: process Requests
+loop Dispatcher::poll
+	activate Dispatcher
+	Dispatcher-->>Dispatcher: Dispatch requests
+end
+deactivate Dispatcher

static/img/diagrams/connection_request.mmd

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+sequenceDiagram
+
+participant HttpServer
+participant HttpServiceHandler
+participant HSHR
+participant State
+participant Dispatcher
+participant Tokio
+
+Note over HSHR, State: HttpServiceHandlerResponse
+
+HttpServer-->>HttpServiceHandler: eventually build...
+alt Protocol::HTTP1
+HttpServiceHandler->>Dispatcher: H1::Dispatcher::new()
+HttpServiceHandler->>State: State::H1(Dispatcher)
+else Protocol::HTTP2
+HttpServiceHandler->>State: State::H2Handshake
+end
+HttpServiceHandler->>HSHR: HttpServiceHandlerResponse::new(State)
+HttpServiceHandler-->>Tokio: StreamService->Tokio::spawn(HttpServiceHandlerResponse as Future)
+
+Tokio->>HSHR: poll()
+alt State::H2Handshake
+HSHR->>Dispatcher: H2::Dispatcher::new(stream,services)
+HSHR->>HSHR: poll()
+else 
+HSHR->>Dispatcher: poll()
+end
+Note over Dispatcher: requests loop

static/img/diagrams/connection_worker.mmd

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+sequenceDiagram
+
+participant ServerBuilder
+participant WorkerClient
+participant Worker
+participant StreamService
+participant HttpServiceHandler
+participant Tokio
+
+ServerBuilder-->>Tokio: spawn(Worker)
+
+Tokio-->>Worker: poll()
+alt WorkerState::Available
+	loop
+		Worker->>WorkerClient: rx.poll_next()
+		WorkerClient->>Worker: WorkerCommand(Conn)
+		Worker->>Worker: check_readiness()
+		alt check_readiness() -> Ok(true)
+			Note over Worker,StreamService: Worker::services[Conn.token]
+			Worker-->>StreamService: call(ServerMessage::Connect(stream))
+			StreamService->>HttpServiceHandler: call(stream)
+			HttpServiceHandler->>StreamService: HttpServiceHandlerResponse as Future
+			StreamService->>Tokio: spawn(HttpServiceHandlerResponse)
+
+		else check_readiness() -> Ok(false)
+			Worker-->>Worker: WorkerState::Unavailable
+		else check_readiness() -> Err(token,idx)
+			Worker-->>Worker: WorkerState::Restarting
+		end
+	end
+end
+
+
+Note over HttpServiceHandler: process connection

static/img/diagrams/http_server.mmd

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+sequenceDiagram
+
+participant HttpServer
+participant ServerBuilder
+participant Worker
+participant StreamNewService
+participant HttpService
+participant HttpServiceResponse
+participant Tokio
+
+
+HttpServer-->>HttpService: build...
+HttpServer->>ServerBuilder: listen(addr,Fn->HttpService)
+ServerBuilder->>StreamNewService: create(addr,Fn->HttpService)
+HttpServer->>ServerBuilder: start()
+ServerBuilder->>Worker: start(StreamNewService)
+
+Worker->>StreamNewService: InternalServiceFactory::create()
+StreamNewService->>HttpService: new_service()
+HttpService->>HttpServiceResponse: HttpServiceResponse::new()
+HttpService->>StreamNewService: HttpServiceResponse as Future
+StreamNewService->>Worker: StreamService(HttpServiceResponse) as Future
+Worker-->>Tokio: spawn(StreamService(HttpServiceResponse)).map(Worker))
+Tokio-->>HttpServiceResponse: poll()
+HttpServiceResponse-->>Tokio: Ready(Worker(HttpServiceHandler))
+
+loop Worker process messages
+	Tokio-->>Worker: poll->Pending...
+	activate Worker
+	Note over Worker: pull messages
+	deactivate Worker
+end