FEATURE: Webhooks and Event for user being granted a badge

Adding a webhook for badge revocation is left for future work as it's relatively rare.

app/services/badge_granter.rb

@@ -410,7 +410,7 @@ class BadgeGranter
   end
 
   def self.send_notification(user_id, username, locale, badge)
-    I18n.with_locale(notification_locale(locale)) do
+    notification = I18n.with_locale(notification_locale(locale)) do
       Notification.create!(
         user_id: user_id,
         notification_type: Notification.types[:granted_badge],
@@ -423,6 +423,10 @@ class BadgeGranter
         }.to_json
       )
     end
+
+    DiscourseEvent.trigger(:user_badge_granted, badge, user_id)
+
+    notification
   end
 
 end