ios: Make notifications "actionable", for mark-as-read etc.

[chrisbobbe]

iOS offers a way to provide action buttons on a notification:

https://developer.apple.com/documentation/usernotifications/declaring-your-actionable-notification-types

It would be helpful to offer buttons like "Mark this message as read" and "Mark whole conversation as read". On #2169 (grouping notifications by conversation), a user wrote:

Related and worth considering alongside grouping: notification actions — at minimum mark-as-read/dismiss — so users can do light triage from the lock screen (clear the conversations they can see are low-priority, keep the rest as unread pointers into the app). Today the only options are open-the-app or swipe away notifications with no effect on unreads, which pushes people toward the mute-everything workaround.

Implementation

See API doc linked above.

Prerequisites

We should implement #1847 first. The natural "success" feedback for a mark-as-read button is the notification disappearing.

[pr3m-kamble]

Hi @chrisbobbe , I'd like to work on this issue with @KrishPatel1605 if it's available.

My plan is to implement actionable notifications on iOS using UNNotificationCategory and UNNotificationAction. I'll add actions such as "Mark as read" and "Mark conversation as read", handle the selected action in the notification response callback, and connect it to the existing read-message API so the conversation state is updated without requiring the app to be opened. Once #1847 is completed, the notification should automatically disappear after a successful mark-as-read action, providing the expected user feedback.

If this approach sounds good, could you please assign this issue to me?

[chrisbobbe]

As I said in the issue description, we should implement #1847 before working on this.

[el-drone]

Of course, usefulness depends on ability to preview message content, and act.  At the very least marking as read, ideally replying.  Although doing the latter without navigating back to the mobile app requires implementing somewhat redundant functionality, while flipping into the app is jarring and breaks the triage flow.