veyron/services/identity: Support for obtaining blessing given an OAuth access token.

Motivation:
The Veyron chrome extension will use the Chrome identity API to obtain an
access token (https://developer.chrome.com/apps/identity#method-getAuthToken)
and then provide that access token to the veyron identity server to obtain
a blessing.

Nick is working on the chrome extension in https://veyron-review.googlesource.com/#/c/3580/,
while this change updates the identity service so that the access token
can be exchanged for a blessing.

Change-Id: I0cd67ed7d523e80992ff5161665211668f6f259d
5 files changed
tree: 1dbba9d7777e73be10588d54baf35b1d9d0b0479
  1. examples/
  2. lib/
  3. products/
  4. runtimes/
  5. security/
  6. services/
  7. tools/