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Response configured with a text message, a document, a text message and another document in this exact order.
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Menu message
Dialogflow provides the ability to return menus where each option results in a clickable button.
To create a menu, the "Card" type message is used (eg. from Facebook or Telegram channel).
The title of the card is used as the header of the menu, while for each single option the relative label and its value are configured, which can be a link to open a new page or a phrase which, if chosen as an answer, will be sent back to the bot.
Finally, if the configured option is a url, an additional parameter is required (that must end with a number corresponding to the position of the option in the sequence of configured options of the menu) called target, to specify where to open the link (_blank, _self, _parent, _top).