Support user migration via `MigrationEnabled` flag in awsconfiguration.json

[patrickcapadmi]

Which AWS Services is the feature request for? Cognito/ com.amazonaws:aws-android-sdk-mobile-client:2.22.2

Is your feature request related to a problem? Please describe. The iOS AWS SDK supports user migration by setting a flag "MigrationEnabled": "YES" in the awsconfiguration.json file, as described here. The same functionality is not supported on Android, leading to workarounds being suggested and put into production, as described in this closed issue.

There is a clear difference between the functionality in the SDKs for each platform: https://github.com/aws-amplify/aws-sdk-ios/search?q=MigrationEnabled https://github.com/aws-amplify/aws-sdk-android/search?q=MigrationEnabled

Describe the solution you'd like Align the functionality in the Android and iOS SDKs in this respect.

Describe alternatives you've considered We're currently making use of the workaround suggested in the closed Android issue linked above, but this is causing duplicate devices to be saved against the user's Cognito account when they sign in post migration. This is not happening with our iOS app signing into the same userpool with the MigrationEnabled flag set.

[abhishekImpressico]

I am also facing the same issue with Android SDK. Is there any workaround for this problem?