Prior to this the content-length could be None instead of 0, the coverage was missing and it could happen that withoutfailing the
right IN-PROGRESS header, the api call would badly failtransition.
This fixes that behavior to actually accept (empty post + IN_PROGRESS false) orAs the coverage was missing, that peculiar case was missed. This fixes it.
fail the request (empty post no IN_PROGRESS at all). And adds the proper tests
around those scenarios.