DEV: Avoid duplicating method attributes in `Auth::Result`.

This ensures that within the class, we have a consistent order of
attributes that is passed to `UsernameSuggester`.

lib/auth/result.rb

@@ -78,7 +78,7 @@ class Auth::Result
   def apply_user_attributes!
     change_made = false
     if SiteSetting.auth_overrides_username? && username.present? && username != user.username
-      user.username = UserNameSuggester.suggest(username || name || email, user.username)
+      user.username = UserNameSuggester.suggest(username_suggester_attributes, user.username)
       change_made = true
     end
 
@@ -139,7 +139,7 @@ class Auth::Result
 
     result = {
       email: email,
-      username: UserNameSuggester.suggest(username || name || email),
+      username: UserNameSuggester.suggest(username_suggester_attributes),
       auth_provider: authenticator_name,
       email_valid: !!email_valid,
       can_edit_username: can_edit_username,
@@ -155,4 +155,10 @@ class Auth::Result
 
     result
   end
+
+  private
+
+  def username_suggester_attributes
+    username || name || email
+  end
 end