Don't try to validate an invalidate token multiple times

I noticed that if a token is invalid because it has expired, we might call `from_token` multiple times. This is because `@current_user` is set to `nil` so won't be cached.

`from_token` calls `HydraPublicApiClient.fetch_oauth_user` which does an API request. Since we might call current_user many times in a controller, we shouldn't be doing a API request from each one.

Since we're currently recording unauthorized errors in Sentry, this often resulted in 3-5 errors being recorded for the same request.

Instead, load the current user once. This might mean in some API calls we're loading the user when we don't need to, but since almost all API actions should validate the current user I don't see this as a problem.

The identifible by cookie file doesn't have this problem, but I've updated it for consistency.

Author: zetter-rpf

app/controllers/concerns/identifiable.rb

@@ -3,12 +3,13 @@
 module Identifiable
   extend ActiveSupport::Concern
 
-  def identify_user
-    token = request.headers['Authorization']
-    User.from_token(token:) if token
+  included do
+    before_action :load_current_user
+    attr_reader :current_user
   end
 
-  def current_user
-    @current_user ||= identify_user
+  def load_current_user
+    token = request.headers['Authorization']
+    @current_user = User.from_token(token:) if token
   end
 end

app/controllers/concerns/identifiable_by_cookie.rb

@@ -4,12 +4,13 @@ module IdentifiableByCookie
   extend ActiveSupport::Concern
   include ActionController::Cookies
 
-  def identify_user
-    token = cookies[:scratch_auth]
-    User.from_token(token:) if token
+  included do
+    before_action :load_current_user
+    attr_reader :current_user
   end
 
-  def current_user
-    @current_user ||= identify_user
+  def load_current_user
+    token = cookies[:scratch_auth]
+    @current_user = User.from_token(token:) if token
   end
 end