When a job is first created, its state is
pending, which makes it still invisible to us and unassignable to a courier.
For a job to be considered as assignable to a courier, it must be submitted by this endpoint.
The only supportable state for submitting a job is
pending, which means that if you try to submit the same job again, you will receive an error as described below since the job will have its state changed after the first attempt.