Open source toolkit for voice services; with special focus to the needs of medium- and low-income countries, scalable services, and interacting with vulnerable populations
The call log is marked as "failed" (I didn't use "canceled" because I couldn't find this state in the code, only in a Twilio handler, but I don't know if this could break some other code that depends on states being a fixed set that, so far, didn't include "canceled")
POST /api/calls/:id/cancel
Needed for https://github.com/instedd/ask/issues/653