feat(django): Gate user identity behind data_collection config

[ericapisani]

Apply the data_collection.user_info setting to Django user identity (id, email, username) collection, giving it precedence over the legacy send_default_pii boolean when explicitly configured. This mirrors the existing behavior for client IP/user info already shipped for Flask, WSGI, and ASGI.

The user extraction logic in _after_get_response is pulled into a shared helper used by both the WSGI and ASGI event processors, and the parametrized send_default_pii/data_collection test matrix is extracted into tests/integrations/django/utils.py for reuse across the WSGI and ASGI test suites.

Refs PY-2583
Refs #6746

[linear-code]

PY-2583

[github-actions]

Codecov Results 📊

✅ 96422 passed | ⏭️ 6370 skipped | Total: 102792 | Pass Rate: 93.8% | Execution Time: 351m 29s

📊 Comparison with Base Branch

Metric	Change
Total Tests	📈 +522
Passed Tests	📈 +492
Failed Tests	—
Skipped Tests	📈 +30

All tests are passing successfully.

✅ Patch coverage is 85.37%. Project has 2513 uncovered lines.
✅ Project coverage is 89.67%. Comparing base (base) to head (head).

Files with missing lines (1)

File	Patch %	Lines
sentry_sdk/integrations/django/init.py	82.86%	⚠️ 6 Missing

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
+ Coverage    89.67%    89.67%        —%
==========================================
  Files          193       193         —
  Lines        24321     24337       +16
  Branches      8572      8586       +14
==========================================
+ Hits         21809     21824       +15
- Misses        2512      2513        +1
- Partials      1397      1399        +2

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