Sign in with Google or any OpenID Connect provider

Authentication is now delegated to Ueberauth and ueberauth_oidcc. You can configure Google sign-in via HIVE_GOOGLE_CLIENT_ID, HIVE_GOOGLE_CLIENT_SECRET, and an optional HIVE_GOOGLE_ALLOWED_DOMAINS allowlist, or any generic OIDC provider via HIVE_OIDC_ISSUER, HIVE_OIDC_CLIENT_ID, HIVE_OIDC_CLIENT_SECRET, and an optional HIVE_OIDC_DISPLAY_NAME. Both can be enabled at the same time, and configured domain allowlists are enforced on the callback.