Creates a test run from the configuration in the request body and starts it
now. Use it when you do not have a saved schedule. The response is the new
test run; use its id to follow, cancel and report on the run.

The easiest way to build runConfigurationEntries is to copy them from a
schedule that already runs the tests you want (GET /v2/schedules/{id}).

Leave out the schedule object to start a test run. If you send it, the request saves
a schedule instead. The response id is a scheduler ID, not a test-run ID.

Requires the TestRun:Create permission. If the request times out, check
the test-run list before you retry: the run may already exist.