Add `cache.hit` data to Django spans

[antonpirker]

Problem Statement

We want to add information on if a configured cache was hit or missed in Django.

See also https://github.com/getsentry/team-webplatform-meta/issues/60

Solution Brainstorm

There are multiple ways to cache data in Django, we probably have to monkey patch Django in various places:

• per-site cache (middlewares) https://docs.djangoproject.com/en/4.2/topics/cache/#the-per-site-cache
• per-view cache (decorator) https://docs.djangoproject.com/en/4.2/topics/cache/#the-per-view-cache
• Template fragment caching (template tag) https://docs.djangoproject.com/en/4.2/topics/cache/#template-fragment-caching
• low level cache api https://docs.djangoproject.com/en/4.2/topics/cache/#the-low-level-cache-api
• async flavor of low level cache api https://docs.djangoproject.com/en/4.2/topics/cache/#asynchronous-support

Maybe just patching the low level cache api will handle all the cases.

[AbhiPrasad]

There's some prior art in https://github.com/tim-schilling/django-debug-toolbar/blob/main/debug_toolbar/panels/cache.py we can look at!

[AbhiPrasad]

@antonpirker mind linking some example transactions that has these values? Screenshots are cool as well 😄