chore(service.naming): schematize django db calls [backport 1.16] (#6358)

Backport 2dbe9cf from #6335 to 1.16.

Django has a separate mechanism for determining service name when using
an underlying database. This change adds the schematized service.naming
to those Django DB calls.

## Checklist

- [x] Change(s) are motivated and described in the PR description.
- [x] Testing strategy is described if automated tests are not included
in the PR.
- [x] Risk is outlined (performance impact, potential for breakage,
maintainability, etc).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
are followed. If no release note is required, add label
`changelog/no-changelog`.
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/)).
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist

- [x] Title is accurate.
- [x] No unnecessary changes are introduced.
- [x] Description motivates each change.
- [x] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [x] Testing strategy adequately addresses listed risk(s).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] Release note makes sense to a user of the library.
- [x] Reviewer has explicitly acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment.
- [x] Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

Co-authored-by: Teague Bick <[email protected]>

Author: github-actions[bot]

ddtrace/contrib/django/patch.py

@@ -106,6 +106,7 @@ def cursor(django, pin, func, instance, args, kwargs):
         else:
             database_prefix = config.django.database_service_name_prefix
             service = "{}{}{}".format(database_prefix, alias, "db")
+            service = schematize_service_name(service)
 
         vendor = getattr(conn, "vendor", "db")
         prefix = sqlx.normalize_vendor(vendor)

tests/contrib/django/test_django.py

@@ -1530,6 +1530,60 @@ def test(client, test_spans):
     assert status == 0, (out, err)
 
 
+@pytest.mark.parametrize("global_service_name", [None, "mysvc"])
+@pytest.mark.parametrize("schema_version", [None, "v0", "v1"])
+def test_schematized_default_db_service_name(
+    ddtrace_run_python_code_in_subprocess, schema_version, global_service_name
+):
+    expected_service_name = {
+        None: "defaultdb",
+        "v0": "defaultdb",
+        "v1": global_service_name or _DEFAULT_SPAN_SERVICE_NAMES["v1"],
+    }[schema_version]
+    code = """
+import pytest
+import sys
+
+import django
+
+from tests.contrib.django.conftest import *
+from tests.utils import override_config
+
+@pytest.mark.django_db
+def test_connection(client, test_spans):
+    from django.contrib.auth.models import User
+
+    users = User.objects.count()
+    assert users == 0
+
+    test_spans.assert_span_count(1)
+    spans = test_spans.get_spans()
+
+    span = spans[0]
+    assert span.name == "sqlite.query"
+    assert span.service == "{}"
+    assert span.span_type == "sql"
+    assert span.get_tag("django.db.vendor") == "sqlite"
+    assert span.get_tag("django.db.alias") == "default"
+
+if __name__ == "__main__":
+    sys.exit(pytest.main(["-x", __file__]))
+    """.format(
+        expected_service_name
+    )
+
+    env = os.environ.copy()
+    if schema_version is not None:
+        env["DD_TRACE_SPAN_ATTRIBUTE_SCHEMA"] = schema_version
+    if global_service_name is not None:
+        env["DD_SERVICE"] = global_service_name
+    out, err, status, _ = ddtrace_run_python_code_in_subprocess(
+        code,
+        env=env,
+    )
+    assert status == 0, (out, err)
+
+
 @pytest.mark.parametrize("schema_version", [None, "v0", "v1"])
 def test_schematized_operation_name(ddtrace_run_python_code_in_subprocess, schema_version):
     expected_operation_name = {None: "django.request", "v0": "django.request", "v1": "http.server.request"}[