refactor(plugin-watson): revive watson plugin with assistantV2

[vanbasten17]

Description

Botonic plugin-watson stopped working and a refactor has been needed to revive it.

Documentation

We need to document that this plugin does not support V1 Assistant anymore. Instead, it supports V2 Assistant.

Now, the plugin options needed are:

• apikey
• url
• assistant_id
• version (Optional: if not provided, '2020-04-01' will be used)

Test

If you want to try the new plugin:

1. Ask @elozano98 for the Watson Assistant options used.
2. Create a bot and link this plugin-watson version to it.
3. Log the data assigned to input in the pre method.
4. Deploy your chatbot.
5. Text to your chatbot with something like: "I want to return this leather jacket".
6. Feel free to experiment with it!

[elozano98]

@vanbasten17 I can not add you to reviewers, but can you take a look at this PR please? 🙏

[vanbasten17]

LGTM, but we must be sure to return the results in the Botonic standard format. Remove @types/axios devDep as the plugin is not in TS yet. Also, too many things happening in index.js. Encapsulate it into a class WatsonOutputParser. And call sth like:

const parser = new WatsonOutputParser()
const nluResults = await parser.toBotonicOutput(input.data)
Object.assign(input, nluResults)

[asastre]

Just 2 small observations (the documentation one I think it should be fixed), the rest LGTM!