app/models/papercat/page.rb
def meta=val
      val = JSON.parse(val) if val.is_a?(String)
      write_store_attribute(:data, :meta, val)
    end
def meta=val
      val = JSON.parse(val) if val.is_a?(String)
      write_store_attribute(:data, :meta, val)
    end
ensure meta always will be saved as json instead of json string