handle 406 / Accept

[tarekziade]

# case 1 : static
@service.post(accept=('text/plain', 'application/json'))
def _service(request):
    ... if accept is in headers and not listed => 406...

# case 2: dynamic
def _get_accept(request):
     """ docstring USED by the doc"""
    ...
    return False, accepted

def _get_accept2(request):
     """ docstring USED by the doc"""
    request.validated['res'] = result
    return True, None

@service.post(accept=_get_accept)
def _service(request):
    ... the decorator calls _get_accept, and returns a 406  if False
    ... get accept can prepare something to be used by the main function to return a response (response.validated['xxx'] = xxx)
    request.response = request.validated['res']