Send Snowplow core events using self-describing events

In the Snowplow documentation for Canonical event model, we have different event types.

However, for the five core events we assign sort of made-up schema urls that they don't exist:

• page_view
• page_ping
• transaction
• transaction_item
• struct
• unstruct

My proposal is to send first four events with unstruct and defined josnSchema. For that, we can add a Boolean to each of these functions to tell it to send with unstruct self-describing events/context instead of the regular payload:

• trackPageView (page_view event + context for browser/device)
• enableActivityTracking (page_ping event + optional context for browser/device )
• addTrans (transaction event + optional context for browser/device )
• addItem (transaction_item context for transaction + optional context for browser/device )

This will help us with some basic field validations and also community users who adapt this new methodology might suffer less later when there is a change in the schema or they want to change the schema or there is a migration plan for atomic.events core table.

Start by reviewing the linked SchemaEnrichment.scala file and the tracker functions named in the issue: trackPageView, enableActivityTracking, addTrans, and addItem. Clarify the self-describing event and schema requirements first; done would mean the four core events use the proposed unstruct format with defined JSON schemas and the relevant behavior is covered by the project’s tests.