Release 5.1.4 - Githubissues

🔧 Native SDK Dependency Updates Only

Update Android SDK from 5.1.6 to 5.1.8

Fix crash with EventProducer's fire events (https://github.com/OneSignal/OneSignal-Android-SDK/pull/2034)
Battery improvements
- Possibly resolves issue #1880 "Egregious levels of battery drain"
- Prevent OperationRepo from continuously pulling when empty (#2033)
- Add backoff to OperationRepo when retrying network calls (#2017)
- Limit refresh User and GET IAMs to foreground (#2036)
Fixes network call batching not waiting the full 5 seconds in most cases to reduce the total number of REST API calls to OneSignal.
external_id skipped and updates stop if something updates the User (such as addTag) shortly before login is called (https://github.com/OneSignal/OneSignal-Android-SDK/pull/2046)
For full changes, see the native release notes

Update iOS SDK from 5.1.3 to 5.1.4

5.1.4 Release Notes
The XCFrameworks in this release is signed to help keep your apps secure
Fix rare scenario where login requests are stuck and prevent the SDK from making updates (https://github.com/OneSignal/OneSignal-iOS-SDK/pull/1398)

This change is