df55f9b189
This change adds an entry to the `links` field of the `/.well-known/webfinger` response. The new entry points to the `appURL` as an OpenID issuer. This is consistent with the output of `/.well-known/openid-configuration`, which also uses the value of `appURL`. This change is required for Tailscale SSO to work, as it uses the OpenID Issuer URL when querying the Tailscale user email during signup/login ([docs](https://tailscale.com/kb/1240/sso-custom-oidc/#webfinger-setup)).