* @param resp response to take authentication values from, might be NULL
* @param auth_infos if auth infos cannot be added for an authenticate header, (I.E case where this method return TRUE),
* a newly allocated belle_sip_auth_info_t object is added to this list. These object contains useful information like realm and username.
* @param auth_infos A newly allocated belle_sip_auth_info_t object is added to this list. These object contains useful information like realm and username.