**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)

apig = aws_stack.connect_to_service('apigateway')
        authorizer = apig.create_authorizer(
            restApiId=self.TEST_API_GATEWAY_ID,
            **self.TEST_API_GATEWAY_AUTHORIZER)
        authorizer_id = authorizer.get('id')
        create_result = apig.get_authorizer(
            restApiId=self.TEST_API_GATEWAY_ID,
            authorizerId=authorizer_id)
        # ignor
        del create_result['ResponseMetadata']
        create_expected = clone(self.TEST_API_GATEWAY_AUTHORIZER)
        create_expected['id'] = authorizer_id
        self.assertDictEqual(create_expected, create_result)
        apig.update_authorizer(
            restApiId=self.TEST_API_GATEWAY_ID,
            authorizerId=authorizer_id,
            patchOperations=self.TEST_API_GATEWAY_AUTHORIZER_OPS)
        update_result = apig.get_authorizer(
            restApiId=self.TEST_API_GATEWAY_ID,
            authorizerId=authorizer_id)
        # ignor
        del update_result['ResponseMetadata']
        update_expected = apply_patch(create_expected, self.TEST_API_GATEWAY_AUTHORIZER_OPS)
        self.assertDictEqual(update_expected, update_result)
        apig.delete_authorizer(
            restApiId=self.TEST_API_GATEWAY_ID,