Expose last message data on the List Conversations endpoint

The List Conversations endpoint returns updated_at, but that timestamp is bumped by any change to a conversation (tagging, assignment, bulk actions), so it can't be used to tell when the last message was actually received. The only way to get a true last-message timestamp today is to follow the last_message link for each conversation; an N+1 pattern that hits rate limits as soon as a contact has more than a handful of conversations (at least for us)

We integrate Front conversations into our internal CRM to show each customer's email history inline. We want to order conversations by their most recent message and show its timestamp, but neither List Conversations nor Search Conversations exposes a last-message timestamp, and the per-conversation follow doesn't scale.

Request

Enrich the list-conversations endpoint with the following fields (shape TBD of course):

1. last_message_timestamp

2. last_message_blurb

3. last_message_author

This would allow us to list them in email inbox style at scale so it can be retrieved in a single request without the N+1 pattern. The timestamp is the more important one to us, but the others would further enhance the UI for ours users so they can glance status more easily.