Expose mandatory option for publish

[pardahlman]

As of version 4.x of the RabbitMQ.Client, the shorthands methods for publish was moved to its own extension class (rabbitmq/rabbitmq-dotnet-client@f8ca49d). RawRabbit should use the publish with all parameters, and make sure that they are configurable in the fluent configuration builder

var client = BusClientFactory.CreateDefault();
client.PublishAsync(new BasicMessage(), configuration: cfg => cfg.WithMandatoryDelivery())