Add support for caching headers primarily ETag/LastModified/If-Non-Match

[prabirshrestha]

I would like to set appropriate caching headers for any responses include html and apis besides file. This improves performance on slow network when fetching it again.

I would like to have similar feature to trillium's caching-headers.

(In case you are wondering why I'm filing issue, I'm trying to port by blog from trillium to salvo https://github.com/prabirshrestha/rblog with the main reason being trillium not support first class error handling compared to salvo)

[chrislearn]

Done

[prabirshrestha]

I can't seem to use this feature. Probably need to add the feature here?

cargo add salvo --features=caching-headers
    Updating crates.io index
      Adding salvo v0.33.0 to dependencies.
             Features:
             + caching-headers
             + cookie
             + test
             - acme
             - affix
             - anyhow
             - basic-auth
             - compression
             - cors
             - csrf
             - extra
             - full
             - jwt-auth
             - logging
             - native-tls
             - openssl
             - proxy
             - rustls
             - salvo_extra
             - serve-static
             - size-limiter
             - sse
             - timeout
             - unix
             - ws
error: unrecognized features: ["caching-headers"]

[chrislearn]

I forgot add it to Cargo.tom. Fixed.

[prabirshrestha]

It is able to compile but don't think it is working as expected.

  let router = Router::new()
      .hoop(extra::caching_headers::CachingHeaders::default())
      .hoop(extra::compression::Compression::default())
      .get(hello_world);

I was expecting curl -vv http://localhost:8080 to return ETag header in the response.

[chrislearn]

I fixed it, please check it again.

[prabirshrestha]

Did you push the changes? I see version 0.33.1 as the latest commit.

[chrislearn]

Please check again, version 0.33.2.

[prabirshrestha]

If it is uncompressed response it works. curl -vv http://localhost:8080.

As soon as I compress it doesn't work. curl -vv --compressed http://localhost:8080. Since most of the content html/css/js/json api are compressed it should support etags when content is compressed.

[chrislearn]

Fixed

[prabirshrestha]

Everything now works as expected. Thanks for fixing the bugs along the way!

Feel free to release a new version so I can consume it directly from crates.io