Improved follow-up with engagement metrics and success status

The user would like a more robust reminder tracking system. Currently, Revel'home lets you consult the history of mailings (e-mail and SMS) and reports delivery problems. However, there is no functionality to track customer engagement (e-mail opens, link clicks) or to mark a reminder as 'successful'. The new functionality should include: 1. **Customer engagement metrics:** Tracking of e-mail opens and link clicks. 2. **Dunning success status:** Ability to manually or automatically mark a reminder as 'successful' based on defined criteria (e.g. customer response, action taken). 3. **Dashboard or report:** Clear display of these metrics to evaluate reminder effectiveness.