VoIP Phone Provisioning Server

We are considering establishing our own auto provisioning server for the voip phones that we sell We sell: Aastra Cisco Gigaset Grandstream Polycom SNOM Yealink Most if not all have provisioning redirection services that would allow us to redirect phones with specified MAC addresses to look to our auto provisioning server for config We are looking at Open Source at the moment. Maybe someone with existing experience and previous project work could provide us with a cost effective solution