Automatically update OpenAPI spec

[nielsvanvelzen]

When a new Jellyfin server version is released the OpenAPI specification is published at https://repo.jellyfin.org/releases/openapi/. Right now updating the SDK requires running the updateApiSpecStable gradle task to download the JSON file and run the generator to create the generated sources.

It would be amazing if we could automate this process by creating a workflow that runs every day/week/? and compares the latest stable specification with the one in the repository. If any changes are found it should update the generated sources, push it to a new branch and create a pull request. We can then validate this PR manually to see if everything works correctly, and make changes to it if required.

[h1dden-da3m0n]

Okay this was way easier than expected due to a AMAZING function by technote-space and it would end up looking something like this: https://github.com/h1dden-da3m0n/jellyfin-sdk-kotlin/pull/1