Diagrams with zoom
------------------

.. mermaid::
   :zoom:

    sequenceDiagram
        participant web as Web Browser
        participant blog as Blog Service
        participant account as Account Service
        participant mail as Mail Service
        participant db as Storage

        Note over web,db: The user must be logged in to submit blog posts
        web->>+account: Logs in using credentials
        account->>db: Query stored accounts
        db->>account: Respond with query result

        alt Credentials not found
            account->>web: Invalid credentials
        else Credentials found
            account->>-web: Successfully logged in

            Note over web,db: When the user is authenticated, they can now submit new posts
            web->>+blog: Submit new post
            blog->>db: Store post data

            par Notifications
                blog--)mail: Send mail to blog subscribers
                blog--)db: Store in-site notifications
            and Response
                blog-->>-web: Successfully posted
            end
        end