[tracking] nginx-compatible http rewrite

[ihciah]

Now the rewrite logic is too simple: it just replaces request's path and query no matter the matched part. Also, since we use http::Request and http::Uri, we will ignore the fragement in url. If it is easy to support, we'd better forward it.

We need to provide this ability like nginx. It can be configured in different with nginx but more clear way, or we can just use nginx's syntax. A rewrite module can also support user modify http headers or return response directly.

This will be an incompatible change. We have to change the way to describe Endpoint.