Generate Java SDK directly from the schema.yml file using OpenAPITools

[tonytamsf]

Using the tooling provided here, we can generate the client SDK's for any language https://github.com/openapitools/openapi-generator

Since I'm working on AntennaPod, I'm generating Java SDK to access the subscription API

I'm capturing progress here https://github.com/tonytamsf/openpodcastapi-java-client-sdk and the steps I'm using here https://github.com/tonytamsf/openpodcastapi-java-client-sdk/blob/main/START.md

cc @keunes