Support custom host portion of Pipedream HTTP endpoints (the "host" in host.m.pipedream.net)

I didn't see any option in the Events to customize the random address that Pipedream generate after create a workflow.
It would be nice if rather than a random hard to remember endpoint address I can change the endpoint to a more friendly one.
Or at least change the address but in pipedream domain.

_Originally posted by @midanilo in https://github.com/PipedreamHQ/pipedream/discussions/1051_