Feature Request: OIDC Support

[linkian209]

I just started using this and I like the simplicity of it. I would love to have OIDC support so I don't need to make any accounts and can just plug this into Pocket ID. I would be happy to try my hand at implementing this if you would like.

[hhhjin]

OIDC support would be a great fit.

I don't currently plan to configure OIDC for the managed Synch deployment, but I'd be happy to review a PR for it. I think it would make sense to make OIDC opt-in based on server-side configuration: when a complete set of OIDC environment variables (discovery URL, client ID, and client secret) is present, the provider is enabled.

This would allow the same implementation to work in both managed and self-hosted deployments without enabling anything by default. The existing browser/device sign-in flow should also work well with OIDC, since authentication can complete in the browser before returning to the device approval page.

Please feel free to open a PR.

[linkian209]

Can do! For future reference, do you prefer people just open PRs with features they'd like; or, would you rather them make an issue here first?

[hhhjin]

For small bug fixes and focused changes, feel free to open a PR directly. For new features, I generally prefer an issue first so we can discuss the direction. However, it's not a hard rule. Feature PRs are welcome too, and I'll review them in good faith.

I've also added this guidance to the CONTRIBUTING.md file: https://github.com/hjinco/synch/blob/main/CONTRIBUTING.md