Swagger or OpenAPI doc for the service

[trajano]

Can we have a OpenAPI doc or swagger.yml file that documents the API? Possibly use redoc to create the apidocs

[crocodile2u]

https://gitlab.com/crocodile2u/athenapdf-openapi - There you can find openapi.yml, which I also tested by generating a PHP client: https://gitlab.com/crocodile2u/athenapdf-client. I can probably file a PR in this repo, but it looks like it's not being updated any more.