[Guide] Object caching with Bedrock (and Trellis) using Redis

[strarsis]

• I've read the guidelines for Contributing to Roots Projects
• This request isn't a duplicate of an existing request
• This is not a personal support request that should be posted on the Roots Discourse community

Summary

Because of some demand in the roots.io discourse (like https://discourse.roots.io/t/use-redis-cache-with-bedrock-and-trellis/15001/1) I wrote a little guide for setting up object caching (Redis) with Bedrock + Trellis:
https://gist.github.com/strarsis/95abe28f4761f489a8a1cc212d5c69e5
This is my first "real" technical guide, so there is probably some room for improvement.

Motivation

nginx microcaching already solves static page caching, but it isn't used for dynamic parts of the site.
Object caching can dramatically increase the performance here, as with WooCommerce and the admin backend.

[swalkinshaw]

Looks useful enough to me 👍 Do you want to do a PR for it?

Personally I'd prefer doing this with memcached since Trellis already installs that by default, but I don't know if the WP plugins are of equivalent functionality/maturity.

[strarsis]

@swalkinshaw: I got some feedback (someone had trouble with a step in the guide), so I need to improve the guide a bit further.
Yes, I can provide a PR for this.