'POST /api/quotas
Creates a new quota.'

@web.expose_api
@web.require_admin
def create(self, trans, payload, **kwd):

    try:
        self.validate_in_users_and_groups(trans, payload)
    except Exception as e:
        raise HTTPBadRequest(detail=str(e))
    params = self.get_quota_params(payload)
    try:
        (quota, message) = self._create_quota(params)
    except ActionInputError as e:
        raise HTTPBadRequest(detail=str(e))
    item = quota.to_dict(value_mapper={'id': trans.security.encode_id})
    item['url'] = url_for('quota', id=trans.security.encode_id(quota.id))
    item['message'] = message
    return item
