Is there an existing issue for this?

• I have read the guide to filing a bug
• I have searched the existing issues

Use case

Any kind of routing that is permission based.

Proposal

• Add optional member in the [NavigationRailDestination] on file [NavigationRailDestinations] class do mark it disabled.
• On the file [navigation_rail.dart] at the class [_RailDestination] add a nullable mark to the VoidCallback onTap member.
• On the file [navigation_rail.dart] at the class [_NavigationRailState] you add [widget.destinations[i].disabled? null :] before the callback that is there right now.

The reason I don't do that myself on a PR is that I don't know the rules. And also I am not sure the best practices when disabling a widget, Flutter conventions etc..., so I guess applying an opacity to help indicate it is disabled.

Thanks.