Issue #, if available

#2193

Description of changes

Adds a new policy template StepFunctionsCallbackPolicy with the necessary permissions for implementing callback patterns.

For more context, I've recently implemented callback patterns with my Step Functions workflow. A Lambda function calls back with the task token along with SendTaskSuccess or SendTaskFailure.

I've originally implemented this (Step Functions - Lambda callback pattern) via SAM Connectors (AWS::Lambda::Function to AWS::StepFunctions::StateMachine), but found the connector policy lacking the necessary permissions for the SendTaskSuccess or SendTaskFailure callbacks.

With connector policies not working for callback patterns, I opted for defining my own policy, which worked.

This is a continuation of a previous attempt to provide a policy template for callback patterns (issue and PR). I've also corrected the Resource scope, which was a requested change that was never resolved in the original PR.

Description of how you validated changes

I validated the changes by updating the translator tests and running make test on Python 3.8.16.

Total test coverage is at 95.73%.

Required test coverage of 95% reached. Total coverage: 95.73%

3961 passed in 267.87s (0:04:27)

Checklist

• Adheres to the development guidelines
• Add/update transform tests
  • Using correct values
  • Using wrong values
• Add/update integration tests

Examples?

Please reach out in the comments if you want to add an example. Examples will be
added to sam init through aws/aws-sam-cli-app-templates.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.