Consider drop of iOS 15

[pylapp]

Context

Ecodesign should be one of the pillar of OUDS. Thus we must support "old" OS versions as best as we can.
Thus, if old versions of OS are supported, old devices are supported, and these old devices may not be replaced by newer ones.
In the end, supporter large range of versions will help customers and users to support same range of versions.

We choose to use SwiftUI as UI framework. However, this framework is a nightmare with iOS 13, a pain with iOS 14 and quite good with iOS 15, this is the reason why we support this version. Even if some features like navigation with navigation stack and use of localized resources like localized string key are available since iOS 16, this is not an issue for a design system library.

However, according to iosref.com, we should maybe reconsider the version 15 of iOS.
Indeed, in opposite of Android where users can still flash newer versions of Android with custom ROM, and where Android versions are not that much stucked to devices, we can see this day the last device not "obsolete" nor "vintage" supporting iOS 15 is iPhone 7 / 7 Plus which is 9 to 10 years old. It begins to be "very old" for smartphones which can have several times battery issues or screen failures for example.

API unlock

• LocalizedStringResource
• NavigationStack

Solution

• Drop iOS 15 for design toolbox
• Maybe drop iOS 15 for Swift Package

Additional issues

• [Refactoring] When drop of iOS 15 for iOS 16, use LocalizedStringResource #681