FEATURE: Send notification by system user for bulk invite

lib/system_message.rb

@@ -9,6 +9,10 @@ class SystemMessage
     self.new(recipient).create(type, params)
   end
 
+  def self.create_from_system_user(recipient, type, params = {})
+    self.new(recipient).create_from_system_user(type, params)
+  end
+
   def initialize(recipient)
     @recipient = recipient
   end
@@ -27,6 +31,20 @@ class SystemMessage
                        subtype: TopicSubtype.system_message)
   end
 
+  def create_from_system_user(type, params = {})
+    params = defaults.merge(params)
+
+    title = I18n.t("system_messages.#{type}.subject_template", params)
+    raw = I18n.t("system_messages.#{type}.text_body_template", params)
+
+    PostCreator.create(Discourse.system_user,
+                       title: title,
+                       raw: raw,
+                       archetype: Archetype.private_message,
+                       target_usernames: @recipient.username,
+                       subtype: TopicSubtype.system_message)
+  end
+
   def defaults
     {
       site_name: SiteSetting.title,