add redirect uri required for idps with rp-initiated logout

docs/docs/documentation/getting-started/authentication/oidc.md

@@ -1,6 +1,6 @@
 # OpenID Connect (OIDC) Authentication
 
-Mealie supports 3rd party authentication via [OpenID Connect (OIDC)](https://openid.net/connect/), an identity layer built on top of OAuth2. OIDC is supported by many identity providers, including:
+Mealie supports 3rd party authentication via [OpenID Connect (OIDC)](https://openid.net/connect/), an identity layer built on top of OAuth2. OIDC is supported by many Identity Providers (IdP), including:
 
 - [Authentik](https://goauthentik.io/integrations/sources/oauth/#openid-connect)
 - [Authelia](https://www.authelia.com/configuration/identity-providers/open-id-connect/)
@@ -23,9 +23,13 @@ Before you can start using OIDC Authentication, you must first configure a new c
 
 2. Configure redirect URI
 
-    The only redirect URI that is needed is `http(s)://DOMAIN:PORT/login`
+    The redirect URI(s) that are needed:
 
-    The redirect URI should include any URL that Mealie is accessible from. Some examples include
+    1. `http(s)://DOMAIN:PORT/login`
+    2. `https(s)://DOMAIN:PORT/login?direct=1`
+        1. This URI is only required if your IdP supports [RP-Initiated Logout](https://openid.net/specs/openid-connect-rpinitiated-1_0.html) such as Keycloak. You may also be able to combine this into the previous URI by using a wildcard: `http(s)://DOMAIN:PORT/login*`
+
+    The redirect URI(s) should include any URL that Mealie is accessible from. Some examples include
 
         http://localhost:9091/login
         https://mealie.example.com/login