Refactor test utilities and enhance ASGI settings

- Cleaned up and standardized assertions in ApiTestMixin for API response validation.
- Updated ASGI settings to use os.environ for setting the DJANGO_SETTINGS_MODULE.
- Removed unused imports and improved formatting in settings.py.
- Refactored URL patterns in urls.py for better readability and organization.
- Enhanced view functions in views.py for consistency and clarity.
- Added .flake8 configuration for linting and style enforcement.
- Introduced type stubs for django-environ to improve type checking with Pylance.

email_service/models.py

@@ -3,11 +3,15 @@ from django.contrib.sites.models import Site
 from core.history import TrackedModel
 import pghistory
 
+
 @pghistory.track()
 class EmailConfiguration(TrackedModel):
     api_key = models.CharField(max_length=255)
     from_email = models.EmailField()
-    from_name = models.CharField(max_length=255, help_text="The name that will appear in the From field of emails")
+    from_name = models.CharField(
+        max_length=255,
+        help_text="The name that will appear in the From field of emails",
+    )
     reply_to = models.EmailField()
     site = models.ForeignKey(Site, on_delete=models.CASCADE)
     created_at = models.DateTimeField(auto_now_add=True)