V4 to v5 upgrade will migrate app ID for wrapper SDKs

[nan-li]

Description

One Line Summary

(Resolves an issue that only affects wrappers) When migrating from v4 to v5, check for a cached app ID from v4 if none are available on v5.

Details

Motivation

• In wrappers, after an app upgrades from player to user model... if the app is not opened yet and a notification is received, there was no app ID detected and initWithContext returns early.
• Now, check for the cached app ID from v4 and use that to continue the init process. This mimics what should happen when using the native SDK directly.
• The reason this is an issue on wrappers is because when an app upgrades, the Application onCreate is automatically called, without needing to open the app. In native SDK clients, their OneSignal initialization code will run here and populate the app ID, setup the user, etc. However, in wrappers, clients don't modify the native code so the onCreate does not set app ID.

Scope

• Using cached app ID from v4 if the app ID has not been set yet after migration
• Affects wrappers
• I aimed to mimic the same behavior as an upgrade using the native SDK, what would happen before the application is opened.

Testing

Unit testing

Manual testing

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

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This change is 

[jinliu9508]

LGTM!

Also verified that Player Model is using the same key to store a legacy app ID.

[nan-li]

Just rebased the branch, no changes.

Looks like a maybe-flaky test added recently is failing the unit tests: https://github.com/OneSignal/OneSignal-Android-SDK/actions/runs/13064783338/job/36455552170?pr=2244

com.onesignal.core.internal.operations.OperationRepoTests > ensure loading in the background thread does not block enqueue FAILED
    io.kotest.assertions.AssertionFailedError: expected:<TERMINATED> but was:<BLOCKED>
        at app//com.onesignal.core.internal.operations.OperationRepoTests$1$2.invokeSuspend(OperationRepoTests.kt:135)
        at app//com.onesignal.core.internal.operations.OperationRepoTests$1$2.invoke(OperationRepoTests.kt)
        at app//com.onesignal.core.internal.operations.OperationRepoTests$1$2.invoke(OperationRepoTests.kt)