* Incremental fixes
* Fix base assignment of async delegate block reference
* Reuse existing memory blocks
* Remove PlaybackStarted child activity
The PlaybackStarted property is unnecessary, since the PlayAudio activity already completes right after playback has started.
* Add GetCallStatus API method
* Prevent variables on composite activities to be overwritten during deserialization
* Remove unnecessary variable declarations
Activity variables will be declared automatically during activity invocation.
* Add XML comments
* Remove unused references arg
* Streamline variable identity assignment
* Fix composite early exit completion
* Move identity assignment to workflow definition service
* Incremental work on Telnyx integration
* Incremental port of Telnyx activities
* Fix polymorphic JSON serialization for webhook data
* Fix IsFirstPass logic
* Fix trigger base to prevent activity auto completion
* Temporarily disable persistent snapshotting provider for testing
* Fix namespaces
* Add method to register activities in bulk using marker type
* Fix Telnyx refit client setup
* Register all Telnyx activities by default
* Incremental work on webhook driven resumption and correlation
* Incremental work on post-bookmark signaling
* Fix bookmark resolution
* Include correlation ID with bookmark
* Fix Telnyx resumption input
* Replace bookmark persisted signal with handler
* Fix SpeakText completion
* Add flow outcomes to SpeakText activity
* Update GatherUsingSpeak and GatherUsingaudio
* Refactor "is first pass" concept
* Fix WebhookEvent activity
* Add HTTP absolute URL provider
* Formatting and small changes
* Various API enhancements
