Add canRequest to Android

[nan-li]

Description

One Line Summary

OneSignal.Notifications.canRequest() has been fixed for Android in https://github.com/OneSignal/OneSignal-Android-SDK/pull/1798, make it available in Flutter SDK.

Details

Motivation

Add OneSignal.Notifications.canRequest() functionality to Android. It was previously iOS-only, with Android always returning false.

Scope

Adds OneSignal.Notifications.canRequest() functionality to Android.

Note that the method OneSignal.Notifications.canRequest() returns whether or not the device has been prompted for push already, and may not indicate on Android whether or not a push prompt will display.

Testing

Manual testing

Testing on Android emulator API 33:

1. New app install and see canRequest = true
2. Prompt for push and accept
3. See canRequest = false which is correct

Affected code checklist

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

Checklist

Overview

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

Testing

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

Final pass

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

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