[webui] Add shorten payload in notifications

- Add shorten_payload_if_necessary method in Notification model to be
sure that a payload is not bigger than the field size in database.
- This should fix openSUSE#4161.

Mobprogrammed with @mdeniz and @DavidKang.

src/api/app/models/notification.rb

@@ -3,9 +3,30 @@ class Notification < ApplicationRecord
 
   serialize :event_payload, JSON
 
+  def initialize
+    super
+    shorten_payload_if_necessary
+  end
+
   def event
     @event ||= event_type.constantize.new(event_payload)
   end
+
+  private
+
+  def shorten_payload_if_necessary
+    return if event.shortenable_key.nil? # If no shortenable_key is set then we cannot shorten the payload
+
+    # NOTE: ActiveSupport::JSON is used for serializing ActiveRecord models attributes
+    overflow_bytes = ActiveSupport::JSON.encode(event_payload).bytesize - 65535
+
+    return if overflow_bytes <= 0
+
+    # Shorten the payload so it will fit into the database column
+    shortenable_content = event_payload[event.shortenable_key.to_s]
+    new_size = shortenable_content.bytesize - overflow_bytes
+    event_payload[event.shortenable_key.to_s] = shortenable_content.mb_chars.limit(new_size)
+  end
 end
 
 # == Schema Information