DASH-IF test vector authorization token provider

Implements the license request authorization protocol described in Dash-Industry-Forum/DASH-IF-IOP#300 and supplies authorization tokens to clients.

Supported authorization mechanisms

1. Predefined tokens.

In the future, other mechanisms may also be added (dynamically generated tokens).

Usage: predefined tokens

1. Edit PredefinedTokens.cs and add your token together with a unique name.
2. Provide clients an <dashif:authzurl> element with the value https://dashif-test-vectors-authz.azurewebsites.net/Authorize/ByPredefinedTokenId/xyz where xyz is the unique name of your token.

Adding more tokens

If you have commit access, just add them. If not, make a pull request.

Updates will go live within a 5 minutes of being committed.