Add public getTags method

[jennantilla]

Description

One Line Summary

Add public OneSignal.User.getTags() method to return local tags for the current user.

Details

Add getTags public method that will return local tags for the current user on both Android and iOS.

Motivation

We removed the getTags method in v5 of the SDKs to discourage use of OneSignal tags as a data store. We have heard feedback from app developers that they have a need for this method still, so we are adding back an implementation to return the local tags.

Scope

Keep note it returns the local tags and not via a server fetch so any tags added mid-session through the REST API will not be reflected.

Testing

Unit testing

None

Manual testing

Successfully call new method getTags on iPhone 15 emulator running iOS 17.0.1 and Pixel 7 running Android 14.

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 

[rgomezp]

@emawby @nan-li @jennantilla why is getTags asynchronous here? This is not consistent with our other SDKs and with the description "returns local tags" https://documentation.onesignal.com/docs/mobile-sdk-reference#gettags

[nan-li]

@rgomezp The call needs to go over the bridge to call the native function and receive the result. It's not consistent with the native SDKs since they don't need to do this.

[rgomezp]

@nan-li I forgot about that limitation. Thanks!