Allow configuring multiple OAuth clients in the same realm

[matthias-stone]

What this does:

Allows different auth portals to use different OAuth clients with the same realm from the same identity provider. See greenpau/caddy-security/issues/307

Why do this:

Currently when multiple sites share an identity provider (eg. Google) with different client IDs they each need to specify a unique realm even though the sites are otherwise unrelated. As the realm forms part of the URL for OAuth callbacks this impacts external configuration as well, requiring clients to allow callbacks to eg. site1.com/oauth/google1, site2.com/oauth/google2, etc. instead of just site1.com/oauth/google, site2.com/oauth/google, etc.. Decoupling the otherwise unrelated configurations simplifies maintenance and set up when using multiple OAuth clients.

What this does not do:

Permit multiple instances of the same identity provider (Google, fb, etc.) within a portal configuration.

How it does this:

Removes requirement for unique realms across all identity providers during initialization.

[github-actions[bot]]

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

[matthias-stone]

I have read the CLA Document and I hereby sign the CLA

[greenpau]

@matthias-stone , I will try getting to this issue soon. Would it be possible to do Google Meet so you can show me your setup?

[matthias-stone]

Sure! Let's set something up.