Rename OIDC strategy from :rauthy to :oidc, update callback path

- Rename AshAuthentication strategy from :oidc :rauthy to :oidc :oidc;
  generated actions are now register_with_oidc / sign_in_with_oidc.
- Update config keys (:rauthy → :oidc) in dev.exs and runtime.exs.
- Update default_redirect_uri to /auth/user/oidc/callback everywhere.
- Rename Mv.Accounts helper functions accordingly.
- Update Mv.Secrets, AuthController, link_oidc_account_live and all tests.
- Update docker-compose.prod.yml, .env.example, README and docs.

IMPORTANT: OIDC providers must be updated to use the new redirect URI
/auth/user/oidc/callback instead of /auth/user/rauthy/callback.

lib/accounts/user.ex

@@ -28,7 +28,7 @@ defmodule Mv.Accounts.User do
 
   @doc """
   AshAuthentication specific: Defines the strategies we want to use for authentication.
-  Currently password and SSO with Rauthy as OIDC provider
+  Currently password and SSO via OIDC (supports any provider: Authentik, Rauthy, Keycloak, etc.)
   """
   authentication do
     session_identifier Application.compile_env!(:mv, :session_identifier)
@@ -52,7 +52,7 @@ defmodule Mv.Accounts.User do
     end
 
     strategies do
-      oidc :rauthy do
+      oidc :oidc do
         client_id Mv.Secrets
         base_url Mv.Secrets
         redirect_uri Mv.Secrets
@@ -88,7 +88,7 @@ defmodule Mv.Accounts.User do
     #       Always use one of these explicit create actions instead:
     #       - :create_user (for manual user creation with optional member link)
     #       - :register_with_password (for password-based registration)
-    #       - :register_with_rauthy (for OIDC-based registration)
+    #       - :register_with_oidc (for OIDC-based registration)
     defaults [:read]
 
     destroy :destroy do
@@ -267,7 +267,7 @@ defmodule Mv.Accounts.User do
       prepare AshAuthentication.Preparations.FilterBySubject
     end
 
-    read :sign_in_with_rauthy do
+    read :sign_in_with_oidc do
       # Single record expected; required for AshAuthentication OAuth2 strategy (returns list of 0 or 1).
       get? true
       argument :user_info, :map, allow_nil?: false
@@ -302,7 +302,7 @@ defmodule Mv.Accounts.User do
               end)
     end
 
-    create :register_with_rauthy do
+    create :register_with_oidc do
       argument :user_info, :map, allow_nil?: false
       argument :oauth_tokens, :map, allow_nil?: false
       upsert? true