chore: [SDK-5307] remove stale compatibility code for iOS below 15

[nan-li]

Description

One Line Summary

Remove the runtime guards and reflection that only existed for iOS 12 through 14, and for iOS 15 on Mac Catalyst. SDK-5307.

Details

Motivation

#1749 raised the deployment target to iOS 15 and #1757 raised Mac Catalyst to match, so every @available(iOS 13.0, *), @available(iOS 14.0, *) and @available(iOS 15.0, *) check is always true, and the performSelector and NSInvocation calls that avoided linking newer APIs at compile time have no reason left to exist.

Scope

• The two Objective-C lifecycle observers and OSRemoteLoggingController register UIScene observers with the UIScene* notification constants instead of string names.
• OSBundleUtils.isAppUsingUIScene and the ephemeral authorization check lose their guards and else branches.
• UIApplication+OneSignal and OSMessagingController read the key window's scene through the typed UIWindowScene API. A nil key window still reads as active, as it did through performSelector.
• The attachment downloader calls NSFileHandle writeData:error: directly, branches on its BOOL result, and drops the pre-13 writeData: fallback.
• createActionForButton: builds UNNotificationActionIcon and calls actionWithIdentifier:title:options:icon: directly, and drops the pre-15 fallback that built the action without an icon. A button without an icon key still passes a nil icon.
• The notification center category references UNTextInputNotificationResponse and UNPushNotificationTrigger directly and reads userText through the typed class.
• OneSignalCoreMocks and the dev app lose the matching #available checks, and the dev app's willPresentNotification always uses the banner and list options.
• Not in this PR: the keyWindow reads, the Xcode-era AUTH_STATUS_EPHEMERAL and provisional defines, the setInspectable: invocation in OneSignalWebView and OSInAppMessageView (Xcode-era reflection under a 16.4 guard that stays), the literal com.apple.UNNotification*ActionIdentifier strings, and the commented-out blocks in the legacy UnitTests target.

Testing

Unit testing

New OneSignalAttachmentHandlerTests calls createActionForButton: with a system icon, a template icon and no icon key, and checks the identifier, title, foreground option and whether icon is set. The old testCreateActionForButtonsWithIcon is commented out with the rest of UnitTests.m, so this path had no live test.

Coverage of the other edits is narrower than it looks. No test host declares UIApplicationSceneManifest, so the existing lifecycle tests run the UIApplication branches only; the scene branches in the two Objective-C observers and in applicationIsActive do not execute under test. OSRemoteLoggingControllerTests injects scene mode and covers the remote logging controller's scene branch, now posting through the UIScene constant. The notification settings tests cover the ephemeral change.

Manual testing

Reduced test plan run serially on an iPhone 17 Pro Max simulator with Xcode 27.0: 356 tests, 0 failures. build-for-testing produces the same warning set as main. OneSignalFramework and OneSignalInAppMessages both build for Mac Catalyst on Xcode 27.0 at the ios15.0-macabi target, which between them compile every touched source file. The dev app builds against the resulting frameworks. Not run on a device.

Affected code checklist

• Notifications
  • Display
  • Open
  • Push Processing
  • Confirm Deliveries
• Outcomes
• Sessions
• In-App Messaging
• REST API requests
• Public API changes

Checklist

Overview

• I have filled out all REQUIRED sections above
• PR does one thing
• Any Public API changes are explained in the PR details and conform to existing APIs

Testing

• I have included test coverage for these changes, or explained why they are not needed
• All automated tests pass, or I explained why that is not possible
• I have personally tested this on my device, or explained why that is not possible

Final pass

• Code is as readable as possible.
• I have reviewed this PR myself, ensuring it meets each checklist item

🤖 Generated with Claude Code

[fadi-george]

Potential issues:

• writeData:error: returns a BOOL, might be cleaner to check that instead of fileHandleError
• OSRemoteLoggingControllerTests still posts "UISceneDidEnterBackgroundNotification" by string, could use UIScene.didEnterBackgroundNotification to match
• NSClassFromString for UNTextInputNotificationResponse / UNPushNotificationTrigger in UNUserNotificationCenter+OneSignalNotifications.m could go too if you want the cleanup to be complete

[nan-li]

Potential issues:

• writeData:error: returns a BOOL, might be cleaner to check that instead of fileHandleError
• OSRemoteLoggingControllerTests still posts "UISceneDidEnterBackgroundNotification" by string, could use UIScene.didEnterBackgroundNotification to match
• NSClassFromString for UNTextInputNotificationResponse / UNPushNotificationTrigger in UNUserNotificationCenter+OneSignalNotifications.m could go too if you want the cleanup to be complete

Thanks. All three are in 6318189

Also rebased onto main after #1757 and added OneSignalAttachmentHandlerTests for the icon paths. Verified on a device with an image attachment and two icon buttons.