Add external_id field to trackEvent Action

[tcgilbert]

This update adds the ability to map a Segment field to Klaviyo's external_id in their create event api.

This comes at the request of the Klaviyo team:

The only other request I have Thomas is that in track/identify mappings for Klaviyo Actions, I’d love to have the ability to add “external_id” in as a profile property. This would help on our side of attributing events in the case where if we wanted to map the segment user_id to an external_id on our end, we could track events without a hard email / phone in the payload (like track calls).

Testing

Tested locally:

[tcgilbert]

waiting for clarity on payload validation from Klaviyo

[tcgilbert]

closing as never got confirmation from Klaviyo