Saga Simplification for 2.0

[jeremydmiller]

I'll be straight up here, I don't like Jasper 1.0's stateful saga approach as well as older competitors, so let's make it better!!!

Ideas:

• Public, concrete classes suffixed with Saga will be the message handlers
• The Saga types will be persisted
• Can have Handle() or Consume() methods
• Static Create() : [SagaType] methods or a constructor for a single argument will be considered to be the initiator methods
• If using a ctor for the initiator, will need other constructors
• Saga persistence providers should use MethodCall as much as possible, or derivatives thereof
• Assume that the Saga id can come off of command messages either through SagaId members, [SagaName]Id, or a member marked as [SagaIdentity]. Keep the fallback to using the saga id header though

Convert Test Harnesses First

For each copy/pasted version of SagaTestHarness

• Copy the Handle() methods on the TSagaHandler to the TSagaState
• Eliminate the TSagaHandler type and type argument

More general tasks:

• Delete the StatefulSagaOf type and all its dependencies
• New convention to discover handlers suffixed as [SomethingSaga]
• Modify Marten middleware to load the actual workflow state as the handler
• Modify the EF Core middleware to load the actual workflow state as the handler

More analysis necessary....

• How do we mark sagas as deleted? COULD return a command that would direct Jasper to do something next
• How do we mark sagas for archival?

[jeremydmiller]

Came out a little different in tasks of course