Django related improvements / feedback

[BYK]

This is a braindump of feedback I got from a friend who tried to use Spotlight with Django:

• It's not clear what Spotlight is or how it works (ref What does this do? #561)
• There's no clear or easy to find guide for Django
• Clearly announce the guiding principle for Spotlight & OSS: it will not require Sentry Cloud ever and it will stay OSI Open Source
• Capturing the error page is nice, want the widget too now (like Django Debug Toolbar) (Make the entrypoint JS usable by other pages #552) (feat(spotlight): Inject Spotlight button on Django sentry-python#3751)
• Click-to-copy for filenames (Add click to copy for file names #548)
• Main use cases:
  • Number of requests
  • Cache usage check / which cache key matched etc - We just need to enable cache_spans in Django integration on SDK side for this (feat(spotlight): Auto enable cache_spans for Spotlight on DEBUG sentry-python#3791)
  • Which view & template was used to render this page -- I think this is captured in trace view so will not action unless I hear otherwise)
  • DB queries (With Sentry SDK v8, not able to get the queries in Spotlight #422)
  • Are there N+1 queries around (Sentry & Django Debug Toolbar does this already)
• Improvements complaints:
  • It's impossible to tell if Spotlight mode is active and working properly. Add something to log output (either tie this to DEBUG setting or SENTRY_DEBUG in the SDK) (feat(spotlight): Add info logs when Sentry is enabled sentry-python#3735)
  • GET/POST/FILES/COOKIES information is not displayed (this is already mostly captured by the SDK) - (feat: Add request and module details to context #544 mostly)
  • User info is missing (the logged in user in Django)
    • Cookies and User info is stripped by default with [send_default_pii](https://docs.sentry.io/platforms/python/configuration/options/#send-default-pii). We can enable this when Spotlight is enabled but then we risk sending this upstream to Sentry if there's a DSN set too. For now, we can limit this to DEBUG mode or lack of DSN for automatic turn-on behavior but looks like we need larger architectural changes for this such as post-scrubbing instead of limiting at the time of collection. (feat: Send PII to Spotlight when no DSN is set sentry-python#3804)
  • Error to trace connection is not clear or easy to follow (Error to trace connection is not clear or easy to follow #551)
  • Transactions under /admin doesn't seem to be captured (intentional by the SDK?) -- We capture these
  • We don't seem to be utilizing profiling info in the UI which may help with the view, template, cache key etc related use cases above

Will be filing individual issues from these as I go.