Add option to disable cache

[pgulley]

While testing the mediacloud stack, the cache sometimes gets in the way of being able to reproduce certain performance bugs. The ability to toggle it off (probably via an environment variable at launch) would go a long way to making this easier to test

[philbudne]

At least for searches, a run-time checkbox (visible only to staff) would be helpful for monitoring historical ingest progress, and doing regular (5 minute?) tests on response time (put into grafana, and triggering alerts if searches fail or take too long).

I did a (VERY) quick look to see how search results are cached, and didn't see it in web-search (but I don't think I looked at the providers library).

I'd be happy to do the backend bits of this!

[philbudne]

I made an attempt to allow disabling of caching in mc-providers here: mediacloud/mc-providers#32

[pgulley]

Posted this in the providers#32, but repeating this here: https://stackoverflow.com/questions/77919265/django-can-i-force-a-request-to-bypass-the-cache-even-if-the-cache-key-already
It seems we could inject a custom version of the 'fetch-from-cache' middleware that would just let us bypass the cache on a given request, which would circumvent the issue where us double-dipping the overview query could confuse the cache. The example here looks for a flag in the requests headers rather than in the request body, which also strikes me as potentially cleaner