Invoking Service Bus function via admin endpoint and passing payload + headers

[SeanFeldman]

The documentation shows how to invoke HTTP-triggered functions. It shows Azure Storage Queues for non-HTTP functions, but that scenario is straightforward because the data posted is transformed into the Storage Queue payload as-is. With ASB, custom headers (application properties) can also be passed in addition to the message payload. Is it possible to achieve passing headers + body for the message? And if 'yes', what's the correct syntax?

Original question from StackOverflow.