Eliminate Failed Calls with Dynamic Connection Capabilities

The addition of dynamic connect for voice apps aims to improve the caller experience by reducing failed calls when the primary line is unavailable. The new functionality works with existing failed call states and introduces four new call states: failed, rejected, unanswered, and busy. When a system uses this feature, Nexmo makes an HTTP call to the event URL in case of a failed state, allowing the web server to respond with an updated NCCO that replaces the original one. This allows for alternative numbers to be tried, improving the overall customer experience.