/// <summary>
/// Creates a <see cref="Event"/> instance out of <see cref="EventDocument"/> instance
/// which can then be posted into IEventProducer. You can use this method to obtain raw event
/// once in order to possibly re-try posting if post fails. The system maintains idempotency of
/// Event posts, therefore a caller may hang to returned Event instance to retry failed posting
/// </summary>
/// <param name="producer">Producer to eventually post event into</param>
/// <param name="evtDoc">EventDocument-derivative instance</param>
/// <param name="headers">Event headers or null</param>
/// <returns>
/// A tuple of (EventAttribute attr, ShardKey partition, Event evt) suitable for
/// making a call to<see cref="IEventProducer.PostAsync(Route, ShardKey, Event, DataLossMode)"/>
/// </returns>
public static (EventAttribute attr, ShardKey partition, Event evt) GetRawEventForDocument(this IEventProducer producer,
EventDocument evtDoc,
JsonDataMap headers = null)
{
var partition = evtDoc.NonNull(nameof(evtDoc)).GetEventPartition();
var eventHeaders = evtDoc.GetEventHeaders(headers);
var rawHeaders = eventHeaders != null?JsonWriter.Write(eventHeaders, JsonWritingOptions.CompactRowsAsMap) : null;
var rawJson = JsonWriter.WriteToBuffer(evtDoc, JsonWritingOptions.CompactRowsAsMap, EVENT_JSON_ENCODING);
var rawEvent = producer.NonNull(nameof(producer))
.MakeNew(CONTENT_TYPE_JSON_DOC, rawJson, rawHeaders);
var attr = EventAttribute.GetFor(evtDoc.GetType());
return(attr, partition, rawEvent);
}