fixes for failed cron maintenance tasks

* update rails scripts for 5.2
* system dmails should be scoped to system
* fix broken url generator in forum notices

app/models/dmail.rb

@@ -110,9 +110,11 @@ class Dmail < ApplicationRecord
       end
 
       def create_automated(params)
-        dmail = Dmail.new(from: User.system, **params)
-        dmail.owner = dmail.to
-        dmail.save
+        CurrentUser.as_system do
+          dmail = Dmail.new(from: User.system, **params)
+          dmail.owner = dmail.to
+          dmail.save
+        end
         dmail
       end
     end

app/views/user_mailer/forum_notice.html.erb

@@ -10,4 +10,4 @@
   <br>
 <% end %>
 
-<p><%= link_to "View topic", forum_topic_path(@forum_topic, :page => @forum_topic.last_page, :host => Danbooru.config.hostname, :only_path => false) %> | <%= link_to "Unsubscribe", maintenance_user_email_notification_url(:user_id => @user.id, :sig => email_sig(@user), :host => Danbooru.config.hostname, :only_path => false) %></p>
+<p><%= link_to "View topic", forum_topic_url(@forum_topic, :page => @forum_topic.last_page, :host => Danbooru.config.hostname, :only_path => false) %> | <%= link_to "Unsubscribe", maintenance_user_email_notification_url(:user_id => @user.id, :sig => email_sig(@user), :host => Danbooru.config.hostname, :only_path => false) %></p>