Add server helpers for creating notification bundle

[ruscoder]

For some cases e.g. testing it's extermely useful to have something like:

def notification_bundle_factory(
    main_resource: r4b.AnyResource,
    subscription_id: str,
    payload_content: Literal["id-only", "full-resource"] = "id-only",
    included_resources: list[r4b.AnyResource] | None = None,
) -> r4b.Bundle:
    now_datetime = "2024-10-31T17:32:46.228024Z"

    host = "http://host.internal/fhir"
    subscription_topic = f"{host}/SubscriptionTopic/{subscription_id}-event"

    def _make_full_url(resource: ResourceProtocol) -> str:
        return f"{host}/{make_reference_str(resource)}"

    subscription_status = r4b.SubscriptionStatus(
        type="event-notification",
        eventsSinceSubscriptionStart="1",
        status="active",
        subscription=r4b.Reference(reference=f"{host}/Subscription/{subscription_id}"),
        topic=subscription_topic,
        notificationEvent=[
            r4b.SubscriptionStatusNotificationEvent(
                timestamp=now_datetime,
                eventNumber="1",
                focus=r4b.Reference(reference=make_reference_str(main_resource)),
                additionalContext=(
                    [
                        r4b.Reference(
                            reference=make_reference_str(resource),
                        )
                        for resource in included_resources
                    ]
                    if included_resources
                    else None
                ),
            )
        ],
    )
    return r4b.Bundle(
        type="history",
        timestamp=now_datetime,
        entry=[
            r4b.BundleEntry(
                request=r4b.BundleEntryRequest(
                    method="GET",
                    url=f"Subscription/{subscription_id}/$status",
                ),
                response=r4b.BundleEntryResponse(status="200"),
                resource=subscription_status,
            ),
            *[
                r4b.BundleEntry(
                    request=r4b.BundleEntryRequest(
                        method="POST" if resource.id == main_resource.id else "GET",
                        url=make_reference_str(resource),
                    ),
                    response=r4b.BundleEntryResponse(
                        status="201" if resource.id == main_resource.id else "200"
                    ),
                    fullUrl=_make_full_url(resource),
                    resource=resource,
                )
                for resource in (
                    [main_resource, *(included_resources or [])]
                    if payload_content == "full-resource"
                    else []
                )
            ],
        ],
    )