Current implementation of HttpServletStreamableServerTransportProvider or HttpServletSseServerTransportProvider needs strict stickyness

Current implementations are holding mcp sessions into a in memory Map https://github.com/modelcontextprotocol/java-sdk/blob/713ee1add0e29d184224aabdf06d024ef30a2754/mcp/src/main/java/io/modelcontextprotocol/server/transport/HttpServletStreamableServerTransportProvider.java#L108
This make it mandatory to have strict stickyness "a la" browser" in a replicated/high availability environement which doesn't exist for agent (and we cannot rely on llm agents to implement this)
The feature could be

• first very simple option an option for HttpServletStreamableServerTransportProvider.Builder to have an option to provide the map (then users can use different tools to have some shared Map)
• create an interface to handle those sessions (with minimum operations such add, get. delete)

Inizia da HttpServletStreamableServerTransportProvider.java intorno alla Map delle sessioni in memoria alla riga 108, quindi esamina HttpServletSseServerTransportProvider per la stessa gestione delle sessioni. Confronta la Map proposta fornita dal builder e un’interfaccia per la gestione delle sessioni, e definisci quali operazioni sono necessarie per deployment replicati senza una stretta persistenza della sessione. Il lavoro è completo quando entrambi i trasporti servlet possono usare lo stato condiviso della sessione tramite un punto di estensione documentato.