Initialise workflow task token manager

[alexiswl]

Use a WorkflowRunStateChangeSync event to run workflows 'within' an AWS Step Functions.

Service 1: TaskTokenManager

1. Listens to any 'WorkflowRunStateChangeSync' event from the OrcaBus
2. Splits the task token out from the event details and stores it in a DynamoDB table indexed by the portal run id
3. Publishes a WorkflowRunStateChange event, with the task token removed

Service 2: Send Task Token Success Events

1. Listens to any 'WorkflowRunStateChange' event with a terminal Status from the OrcaBus
2. Looks up the portal run id in the DynamoDB table to get the task token (if it exists)
3. Sends either a TaskTokenSuccess or TaskTokenFailure event

An attribute might look like this

{
  "EventBusName": "OrcaBusMain",
  "Source": "Whatever",
  "DetailType": "WorkflowRunStateChangeSync",
  "Detail": {
    "portalRunId": "...",
    "taskToken": "task token",
    ...
    "payload": {
      "data": {}
    }
  }
}

One can generate the detail from the source with the following AWS Step Functions Code

{
  "QueryLanguage": "JSONata",
  ...
  "States": {
    "Run Workflow": {
      "Type": "Task",
      "Resource": "arn:aws:states:::events:putEvents.waitForTaskToken",
      "Arguments": {
        "Entries": [
          {
            "Detail": "{% $merge(\n  [\n    {\n      \"taskToken\": $states.context.Task.Token\n    }, \n    $workflow_run_state_change_event_obj\n  ]\n) %}",
            "DetailType": "WorkflowRunStateChangeSync",
            "EventBusName": "OrcaBusMain",
            "Source": "Whatever"
          }
        ]
      },
      "Next": ...
    }
  }
}

[victorskl]

Please on hold merge this PR until 0.3.0 release wrap up.