Feature set language callbacks

[tanaynigam]

Description

Line Summary

Add set language callback

Details

Motivation

The feature allows the user to use the onSuccess and onFailure callbacks for setLanguage method

Public API Changes

The documentation will need to be updated for Android to provide these new methods

• Add OSDeviceInfoCompletionHandler
• Add setLanguage(String, OSDeviceInfoCompletionHandler)

Testing

Unit Tests

Add TestSetLanguageHandler to set up callbacks for setLanguage
Add following Unit test cases

• Add shouldSetLanguageWithResponse to test for success callback
• Add shouldFailToSetLanguageWithResponse to test for failure callback

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This change is 

[jkasten2]

Reviewed 5 of 5 files at r1, all commit messages.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @nan-li and @tanaynigam)

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OneSignalSDK/onesignal/src/main/java/com/onesignal/OneSignal.java, line 232 at r1 (raw file):

   }

   static class OSDeviceInfoError {

Since OneSignalStateSynchronizer produces this internal type it should be defined there. Along with OSDeviceInfoCompletionHandler below.

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OneSignalSDK/unittest/src/test/java/com/test/onesignal/MainOneSignalClassRunner.java, line 2810 at r1 (raw file):

      // now test to make sure the handler still fires for a call to
      // setLanguage() that doesn't modify existing language (no JSON delta)

This comment isn't accurate, above the language is "fr" and below it is "es" so there is a change.

[jkasten2]

Reviewed 4 of 4 files at r2, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @nan-li and @tanaynigam)