Planned features

[kbalt]

• [x] Better call management (cancellation on server & client) (sip-ua's client side support is rather lacking, since I've not yet needed it)
• [ ] Server side digest authentication
• [x] SDP negotiation / RTP media sessions (worked on in https://github.com/kbalt/ezk-media)

[jason-shen]

nice to see the media stuff is in now, good work @kbalt