Playready persistent license support

[sridhard]

Have you read the FAQ and checked for duplicate open issues? Yes. I have checked the issues

What version of Shaka Player are you using? 4.2.1

Can you reproduce the issue with our latest release version? yes

Can you reproduce the issue with the latest code from main? yes

Are you using the demo app or your own custom app? custom app, In demo app files with only PR are not working

If custom app, can you reproduce the issue using our demo app? yes

What browser and OS are you using? windows-10, edge browser

For embedded devices (smart TVs, etc.), what model and firmware version are you using? NA

What did you do? Try to save the file offline (With only playready in manifest)

What did you expect to happen? Offline save and play should be success

What actually happened? Shaka player not supporting offline file for playready

Now shaka player supports com.microsoft.playready.recommendation key system. I have read shaka-player issues and also dash.js issues. Also as per the docs com.microsoft.playready.recommendation supports persistent licenses. but shaka player is not able to support it