Expose Snooze functionality via a Web API

Is your feature request related to a problem? Please describe.

Nextcloud Mail's Snooze feature is great, it's a much-needed feature that IMAP unfortunately doesn't provide out of the box.

Currently, it is only available via Nextcloud Mail's own UI, and there is no compatibility with other software providing similar functionality.

Describe the solution you'd like

It would be awesome if other email clients (such as Thunderbird, via addons) could profit from Nextcloud Mail's server-side Snooze functionality and provide their own UI to use Nextcloud Mail as a Snooze backend.

So Nextcloud Mail would have to expose a Web API that allows clients to snooze and unsnooze messages and to query messages for whether they are snoozed and until when.

Describe alternatives you've considered

I'm currently using a Thunderbird addon but that only works on Desktop, for mobile I have to use Nextcloud Mail's UI. Both can share the same Snoozed folder, but they are not compatible in the sense that a message snoozed with one client will not be shown as snoozed by the other.

Additional context

No response

No files or tests are named. Start by locating the existing Snooze UI and server-side functionality, then review how this project exposes APIs. Done means clients can snooze and unsnooze messages and query whether they are snoozed and until when, with state shared across clients.