serialize metadata attributes

app/models/concerns/metadatable.rb

@@ -3,6 +3,10 @@
 module Metadatable
   extend ActiveSupport::Concern
 
+  included do
+    serialize :metadata, HashSerializer
+  end
+
   def get_metadata_value_of key
     get_metadata_values_of(key).first
   end

app/serializers/hash_serializer.rb

+class HashSerializer
+  def self.dump(hash)
+    hash.to_json
+  end
+
+  def self.load(hash)
+    (hash || {}).with_indifferent_access
+  end
+end
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