Consider documenting "shared session/transaction" concept

[timbussmann]

Many transports either have shared transactions or even shared sessions when using Sagas or the Outbox. While there are some persistence specific parts, e.g.

• https://docs.particular.net/persistence/mongodb/#transactions-shared-transactions
• https://docs.particular.net/persistence/ravendb/#shared-session
• https://docs.particular.net/persistence/cosmosdb/transactions
• https://docs.particular.net/persistence/dynamodb/transactions

there might be value explaining the concept behind this, e.g. via a diagram like this:

sequenceDiagram
    Queue->>NSB: ReceiveMessage
    NSB->>Storage: Open session
    NSB->>Application: Invoke message handler
    Application->>Storage: Store business data
    Application-->>NSB: message handler finished
    NSB->>Storage: Store workflow/outbox data
    NSB->>Storage: Commit transaction
    NSB-xStorage: Close session
    NSB-->>Queue: Ack message