feature: Ingest OpenAPI specifications from Amazon API Gateway

[niallthomson]

🔖 Feature description

Using Backstage as an API catalog is a common use-case with its support for OpenAPI specifications. Today users will tend to "manually" sync the OpenAPI specification to Backstage through something like a build/deployment tool.

This feature would allow Backstage users to "automatically" sync OpenAPI specifications directly from Amazon API Gateway, removing the need for separate process.

🎤 Context

See here for similar solution from AWS partner ReadMe

https://aws.amazon.com/blogs/apn/integrating-readme-with-amazon-api-gateway-to-keep-your-developer-hub-up-to-date/

Use-case:

https://aws.amazon.com/blogs/opensource/how-traveloka-uses-backstage-as-an-api-developer-portal-for-amazon-api-gateway/

API call to export OpenAPI specification:

https://docs.aws.amazon.com/apigateway/latest/api/API_GetExport.html

✌️ Possible Implementation

No response