Add apiai option as an alternative to botkit studio

[ear-dev]

When the env apiai_token='' is set, the bot will use the dialogflow middleware to talk to dialogflow instead of botkit studio.

We have been configuring dialogflow intents with a custom payload which represents our RC attachments. In this way we can send any json format we want, to describe our rich message content.

This PR also includes a middleware.format.use function which knows how to unpack the response from dialogflow and add the attachment to the RC message object.

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✅ ericrosenthal
✅ ear-dev
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[arthurTemporim]

Hi @ear-dev , thank you for this PR

Now the .env file is following the Rocket.chat pattern:

.env

Can you please update this PR to the new environment variables names?

I noticed too that your botkit studio token is in your .env file and add your token to this repository it's not good because everyone that starts to use this example will be using your bot, so it's good to remove it.

token

Please add an explanation to apiai in the README too, if you have any trouble, please let me know.

Thank you very much 👍

[ear-dev]

Thanks @arthurTemporim!

I've fixed the PR.... can you take another look.

[ear-dev]

@arthurTemporim @Sing-Li I am updating our apiai botkit implementation to use dialogflow v2. format.use has to change a bit, as does the authentication method. Do you want this PR to be backwards compatible, or just support v2 only, since dialogflow is moving in that direction?

[Sing-Li]

I think keeping it v2 only is fine. Thanks.