Add a way to dismiss all error pop-up notificaions

[laikoni]

Is your feature request related to a problem? Please describe.
I copied a folder with several hundred pictures to a different folder that already contained most but not all of those pictures. Thus, I got several hundred "Could not copy ..., target exists" pop-ups:

So far, those need to be dismissed one by one as they do not seem to disappear after a while. As a workaround I found that they are cleared when I reload the site, though that's not very user friendly.

Describe the solution you'd like
It would be nice to have way to dismiss all of these pop-ups, potentially with a "Dismiss all" appearing above when more than one pop-up is displayed.

Describe alternatives you've considered
Another possibility would be to let these pop-ups vanish after a short amount of time. However if they are actually displaying important information, it can be frustrating when the error message disappears before you got the chance to copy it.

[ChristophWurst]

well, this is possibly something to still fix in the app that uses this library. the app could keep track of what notifications are shown and then act when too many are generated and similar

I don't see how this library can help with that. keeping book of the shown notifications and then automatically hiding some sounds potentially dangerous. let's fix the cause and not the symptoms.

[TheFatherMind]

I vote we fix BOTH...
I have 10,000 repeat notifications I would like to clear. A "dismiss" all would be VERY helpful about now...

[ChristophWurst]

fyi dialogs toasts != desktop client notifications

please file a feature request at https://github.com/nextcloud/desktop