Creating json web token for sign in with apple.
You should pass result key to "client_secret" parameter as a string.
Script usage:
sudo gem install jwt ruby generator.rb
a key file: AuthKey_KEY_FILE_NAME.p8 (obtained from https://developer.apple.com/account/resources/authkeys/list)
a bundle identifer (for clients) or service id (web platforms: https://developer.apple.com/account/resources/identifiers/list/serviceId)
your apple team id - (You can find at membership tab)
You can check https://medium.com/@erdikank/how-to-verify-sign-in-with-apple-token-2601c72a3f4d for full tutorial.