Generalize automatic login redirect beyond OIDC-only setups

Source: outline/outline#13972 · opened by @jdk-21

Current behavior

An automatic redirect to the login provider is only performed when OIDC is the only enabled provider.

Proposal

Always redirect automatically when exactly one authentication provider is enabled, regardless of provider type. To opt out:
OIDC_DISABLE_REDIRECT currently disables the redirect, but its name is OIDC-specific.

Two options:
1. Rename it to AUTH_DISABLE_REDIRECT (cleaner, but a breaking change).
2. Keep OIDC_DISABLE_REDIRECT and add AUTH_DISABLE_REDIRECT as the generic variable. The old one stays as a deprecated alias.

I'm happy to provide a pull request for this.

12 hours ago