Unit Testing Framework for Saga

[briansain]

Is your feature request related to a problem? Please describe.
No

Describe the solution you'd like
There is a unit test framework for testing aggregates, but not for sagas. The documentation says that sagas are coming, but with the transition of the project that got left behind. I'd like to see this feature added so unit testing with akkatecture sagas is as clean as testing with aggregates.

Describe alternatives you've considered
Testing can currently be with just the Akka dotnet TestKit, but it could potentially not follow the flow that was setup with aggregate testing and it's harder to do by hand.

Additional context
Need to discuss how to do this because it is a more complex scenario than aggregate testing.