Feature: ask for notification permission

[elemanhillary-zz]

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Description

This pull requests ask macOS for notification permission somehow to get macOS prompt user if he wants to allow notifications even if signal messenger has notifications disabled in preferences.

This solves #3653

[scottnonnenberg-signal]

My testing indicates that the value for Notification.permission doesn't reflect the macOS-level notification permission for Signal. Nor does asking for permissions display any kind of UI. How did you test this?

[elemanhillary-zz]

My testing indicates that the value for Notification.permission doesn't reflect the macOS-level notification permission for Signal. Nor does asking for permissions display any kind of UI. How did you test this?

My testing indicates that the value for Notification.permission doesn't reflect the macOS-level notification permission for Signal. Nor does asking for permissions display any kind of UI. How did you test this?

I made sure that I don't have Signal App in the notification centre so that on starting the application it should ask for notifications permission

[scottnonnenberg-signal]

How did you ensure that Signal was not in the notification center?

[elemanhillary-zz]

How did you ensure that Signal was not in the notification center?

Went into system preferences(MacOs catalina) and went to Notification center

[scottnonnenberg-signal]

Again, my testing indicates that this doesn't work. Notification.permission was set to 'granted' even with macOS settings had turned off notifications. Closing.