In the latter case you just probe, for instance if you’re a password manager and you have a password for site A you hit A/.well-known/change-password and if they returns something you can surface a change password link to your user.
The one you found is for OIDC provider discovery (https://openid.net/specs/openid-connect-discovery-1_0.html#P...) so someone tells you they want to log in via Google, you hit that endpoint, and it lets you setup Google as an oidc provider rather without needing to hard-code providers. Even if you just want to support Google as a provider, you hit that and you get the entire configuration rather than have to hunt down the same information in the docs.
That said, I still find it very bizzare that it's so hard to find a tangible example to see how it is in practice.
The rfc has none. Another spec including the use of it has none. In the end only completed service provider/implementers show it.
Before programmatic access happens, it needs to be written by a human. Yet the whole thing feels so human-unfriendly.
Perhaps I am biased robots.txt sets a high bar on how easy it is to find and work with?
It's a JSON array of public keys which you can use to validate a JWT which is what an OIDC token is.
Making it an array means you can rotate keys whenever but the validator is typically caching the public keys.
https://www.hanko.io/blog/understanding-jwks
Actually... found it https://datatracker.ietf.org/doc/html/rfc6749
And here's a PHP implementation that is perfect. https://github.com/thephpleague/oauth2-client