**Overview**

In AWS it is possible to trigger step functions through an API Gateway integration, see https://docs.aws.amazon.com/step-functions/latest/dg/tutorial-api-gateway.html

Similar integrations already occur within localstack, however the step function URIs are notably missing. See lines 66-88 of https://github.com/localstack/localstack/blob/master/localstack/services/apigateway/apigateway_listener.py



┆Issue is synchronized with this [Jira Bug](https://localstack.atlassian.net/browse/LOC-107) by [Unito](https://www.unito.io/learn-more)

client = aws_stack.connect_to_service('apigateway')
        response = client.create_rest_api(name='my_api', description='this is my api')
        rest_api_id = response['id']
        dummy_rest_api_id = '_non_existing_'
        _name = 'testModel'
        description = 'test '
        content_type = 'application/json'
        # succe
        response = client.create_(
            restApiId=rest_api_id,
            name=_name,
            description=description,
            contentType=content_type,
        )
        self.assertEqual(response['name'], _name)
        self.assertEqual(response['description'], description)
        try:
            client.create_(
                restApiId=dummy_rest_api_id,
                name=_name,
                description=description,
                contentType=content_type,
            )
            self.fail('This call should not be successful as the rest api is not valid.')
        except ClientError as e:
            self.assertEqual(e.response['Error']['Code'], 'NotFoundException')
            self.assertEqual(e.response['Error']['Message'], 'Invalid Rest API Id specified')
        try:
            client.create_(
                restApiId=dummy_rest_api_id,