**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)

origin = 'localhost'
        result = requests.options(url, headers={'origin': origin})
        self.assertEqual(result.status_code, 200)
        self.assertTrue(re.match(result.headers['Access-Control-Allow-Origin'].replace('*', '.*'), origin))
        self.assertIn('POST', result.headers['Access-Control-Allow-Methods'])
        custom_result = json.dumps({'foo': 'bar'})
        
        result = requests.get(url)
        self.assertEqual(result.status_code, 200)
        expected = custom_result if int_type == 'custom' else '{}'
        self.assertEqual(json.loads(to_str(result.content))['data'], expected)
        
        data = json.dumps({'data': 123})
        result = requests.post(url, data=data)
        self.assertEqual(result.status_code, 200)
        expected = custom_result if int_type == 'custom' else data
        self.assertEqual(json.loads(to_str(result.content))['data'], expected)
        
        data = 'test=123'
        ctype = 'application/x-www-form-urlencoded'
        result = requests.post(url, data=data, headers={'content-type': ctype})
        self.assertEqual(result.status_code, 200)
        content = json.loads(to_str(result.content))
        headers = CaseInsensitiveDict(content['headers'])
        expected = custom_result if int_type == 'custom' else data
        self.assertEqual(content['data'], expected)
        self.assertEqual(headers['content-type'], ctype)
        
        proxy.stop()
    def test_api_gateway_lambda_proxy_integration(self):