GeezerVison

Refs #6402

cache.add() was a blind spot. cache.set() emitted cache.put, cache.add() emitted nothing. kinda odd for a normal Django cache write path.

Repro

from django.core.cache import cache
import sentry_sdk
from sentry_sdk.integrations.django import DjangoIntegration

sentry_sdk.init(
    integrations=[DjangoIntegration(cache_spans=True)],
    traces_sample_rate=1.0,
)

with sentry_sdk.start_transaction(name="t", op="test"):
    cache.add("k", "value")

Before this patch: no cache span.
After this patch: one cache.put span for cache.add().

What changed

• instrument cache.add()
• treat it as cache.put
• add a regression test for static + stream mode

Tested

• tox -e py3.12-django-v4.2.30 -- -k test_cache_spans_add

I also checked a wider Django cache test slice, but this env doesnt have the repo's local Postgres test service, so the db-marked Django tests bail early.