Identity

Treat state-mismatch errors as no-op. This allows downstream apps to gracefully ignore state-mismatch error.

* Automatically renew signed-in session (13, 11, 12)

* Enhancement: `log_in(..., prompt=...)` accepts [prompt values defined in OIDC specs](https://openid.net/specs/openid-connect-core-1_0.html#AuthRequest). This is useful when you want to force user to login or provide user a change to switch account.

* API changed since 0.1.0. And now the documentation is available in [project's README](https://github.com/rayluo/identity#identity-library) and on [ReadTheDocs](https://identity-library.readthedocs.io/).
* Sample coming soon.

The first prototype of Identity library. Docs and sample are coming soon.