update rest api no-cache example code

[jazzsequence]

Fixes #8675

Summary

Bypassing Cache with HTTP Headers - Updates the code snippet example for bypassing cache headers for rest requests

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[stevector]

@jazzsequence did you try this code on a site on the platform? If so, I'll approve/merge.

[jazzsequence]

@stevector I haven't yet. I want to do that before we merge.

[jazzsequence]

@stevector
So, I think the approach is correct -- in that we should not semantically be performing an action inside something intended to filter content -- however, the solution does not work. I think this is actually related to this issue (related community slack conversation). The underlying issue being it doesn't matter if the application sends no-cache headers to the CDN, the CDN does not change its behavior when it receives those headers and continues to serve cached copies.

Additionally, implementing the suggested change causes 502 errors if a REST API endpoint does not have a cached copy yet. For example, if I go to /wp-json/wp/v2/pages/ on a site where I haven't already hit that endpoint, I get a 502. However, if I remove the code and visit that endpoint and then re-enable it, I will always get the cached version of that endpoint (until the cache expires). I think the actual solution here is to remove this recommendation until the underlying issue is resolved (and open a docs issue that we come back to this if/when that issue is resolved). It's currently sitting inside a feature request (FEAT-1420).

[jazzsequence]

lol it would help if I used the right header name (Cache-Control not Cache Control) in my test code 🙃
Nevermind everything, this is good 😂