user name changes: don't create feedback or modaction.

Don't create a neutral feedback, create a mod action, or dmail the user
after changing a user's name. The name change is already recorded in
/user_name_change_requests, so creating feedbacks and mod actions is
redundant. They also expose private information (when a user deletes
their account, old name changes aren't supposed to be visible any more).

app/models/user_name_change_request.rb

@@ -6,7 +6,7 @@ class UserNameChangeRequest < ApplicationRecord
   validates :desired_name, user_name: true
   validates_presence_of :original_name, :desired_name
 
-  after_create :approve!
+  after_create :update_name!
 
   def self.visible(viewer = CurrentUser.user)
     if viewer.is_admin?
@@ -18,12 +18,8 @@ class UserNameChangeRequest < ApplicationRecord
     end
   end
 
-  def approve!
-    user.update_attribute(:name, desired_name)
-    body = "Your name change request has been approved. Be sure to log in with your new user name."
-    Dmail.create_automated(:title => "Name change request approved", :body => body, :to_id => user_id)
-    UserFeedback.create(:user_id => user_id, :category => "neutral", :body => "Name changed from #{original_name} to #{desired_name}")
-    ModAction.log("Name changed from #{original_name} to #{desired_name}",:user_name_change)
+  def update_name!
+    user.update!(name: desired_name)
   end
 
   def not_limited