vonage-dotnet-sdk v5.4.0

New

Adds the Async Pattern to the Vonage SDK. All methods that were synchronous have both a sync and async flavor. To use the async method simply add Async to the end of the old method name - e.g. SendAnSmsAsync

Adds new APIs for making Phone calls with the Voice API, specifically CreateCall has two new overloads which support either two phone numbers (to and from) and an NCCO, or a to endpoint and from number and NCCO

Fixes

Fix enumeration issue for Verify workflows

Some minor null checking.