Destination for Kevel Audience

[tiagoboldt]

This Pull Request introduces an integration with Kevel Audience, a second product from Kevel. To avoid confusion, the current Kevel plugin that integrates through Kevel UserDB, still in Beta, was moved to the kevel-userdb folder, and the documentation was clarified.

Testing

The app was tested locally with identify and track events to verify both properties and audiences are sent. Some unit tests briefly verify the implementation.

• Added unit tests for new functionality
• Tested end-to-end using the local server
• [Segmenters] Tested in the staging environment - not done, not quite sure how to do this.

[joe-ayoub-segment]

Hi @tiagoboldt thanks for raising this PR.

I think the proposed changes warrant a face to face meeting. Would you be able to schedule a call with me here please?
https://calendly.com/joe_ayoub/

Best regards,
Joe

[joe-ayoub-segment]

Moved the PR to an internal PR so I could make some minor wording changes.
I also retained the original slug, baut kept the new name for the Kevel-DB Destination.

Here is the new PR.
#1910

I'll deploy the code as is, however I think it would be useful to add a 'testAuthenication' function to validate the settings. This function gets called after the user inputs and saves the Settings for the Integration. There's plenty of examples of how to do this in the codebase.