Proposal to use Souin as an HTTP cache system

[darkweak]

Issue Description

Hello there, first thank you for your awesome work on echo and the ecosystem.
I would know if it would be accepted if I apply for integrate the Souin HTTP cache system as an available cache provider into echo ?
It supports a distributed and not distributed storage systems using Olric (the distributed one) and Badger (the non distributed), it suits the RFC-7234 and supports the Cache-Status HTTP header.
I already wrote a middleware handler for Træfik, caddy (which one will replace the official one soon) and for Tyk.
Souin can invalidate the CDN placed on top of your stack such as Cloudflare, Fastly, ... and can set the returned data into the CDN cache to be served as fast as possible.
Open to discuss about it with you ✌️.

[aldas]

Hi, middlewares with external dependencies usually go in https://github.com/labstack/echo-contrib but you are probably better off creating completely separate repo for Souin as you can iterate in separate repo way faster.

For visibility we could create list off external/3rd-party middlewares in echo-contrib readme.md and maybe somewhere in Echo website

[darkweak]

Hi @aldas thank you for your answer, I'll setup a working poc this week-end and apply a PR on the contrib repository.

It would be great to create the 3rd-party middlewares in the Echo website imho.