**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)

self.create_lambda_function(lambda_name)
        lambda_uri = aws_stack.lambda_function_arn(lambda_name)
        # creat
        api = apigw_client.create_rest_api(name='test-api', description='')
        api_id = api['id']
        root_res_id = apigw_client.get_resources(restApiId=api_id)['items'][0]['id']
        # creat
        authorizer = apigw_client.create_authorizer(
            restApiId=api_id,
            name='lambda_authorizer',
            type='TOKEN',
            authorizerUri='arn:aws:apigateway:us-east-1:lambda:path/ \
                2015-03-31/functions/{}/invocations'.format(lambda_uri),
            identitySource='method.request.header.Auth'
        )
        # creat
        is_api_key_required = True
        method_response = apigw_client.put_method(
            restApiId=api_id, resourceId=root_res_id, httpMethod='GET', authorizationType='CUSTOM',
            authorizerId=authorizer['id'], apiKeyRequired=is_api_key_required
        )
        self.assertEqual(authorizer['id'], method_response['authorizerId'])
        
        lambda_client = aws_stack.connect_to_service('lambda')
        lambda_client.delete_function(FunctionName=lambda_name)
        apigw_client.delete_rest_api(restApiId=api_id)
    # =====================================================================
    # Helper methods
    # =====================================================================
    def connect_api_gateway_to_kinesis(self, gateway_name, kinesis_stream):