[Feature] Email Event Enrichment

### Is there an existing feature request for this?

- [X] I have searched the existing issues

### Describe the Feature

Whenever an event enters as emailOpen or emailClicked - the channel_id, channel_name, etc. all come in as NULL values making it difficult to query. This data only comes in on the emailSent event. Additionally, the transactional_data that triggered these emails is only included on the emailSent event. So I need to end up joining the message_id on each emailClick and emailOpen event to enrich the columns with the data.

### Describe alternatives you've considered

Somehow it would be great to include the transaction_data from the emailSent event on triggered emails inside the emailOpen and emailClick. I don't know the best approach to this... adding a whole new column: triggered_transaction_data OR appending the transaction_data of the emailClick and emailOpen.... open to ideas.

### Are you interested in contributing this feature?

- [X] Yes.
- [X] Yes, but I will need assistance and will schedule time during your [office hours](https://calendly.com/fivetran-solutions-team/fivetran-solutions-team-office-hours) for guidance.
- [X] No.

### Anything else?

Would love to see this added :)

Start by tracing the transformation models for emailSent, emailOpen, and emailClicked, focusing on message_id, the NULL channel fields, and transactional_data. Done means the approach is defined and open/click events expose the relevant emailSent enrichment consistently, with validation for the resulting queries.

Written by the indexing model from the issue text.