Sentinel in Tower

Implement Sentinel as a service in Tower.

In the example directory, we provide an example for tonic.

Why Setinel?

Though tonic::transport::channel::Endpoint does provide methods like rate_limit() to construct middleware like tower::limit::rate::RateLimitLayer(), Sentinel provides more general and flexible high-reliability services.

And Sentinel will be the default traffic governance implentation for the OpenSergo standard.