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/admin.py

@@ -1,36 +1,39 @@
 from django.contrib import admin
 from django.contrib.sites.models import Site
-from django.contrib.sites.shortcuts import get_current_site
 from .models import EmailConfiguration
 
+
 @admin.register(EmailConfiguration)
 class EmailConfigurationAdmin(admin.ModelAdmin):
-    list_display = ('site', 'from_name', 'from_email', 'reply_to', 'updated_at')
-    list_select_related = ('site',)
-    search_fields = ('site__domain', 'from_name', 'from_email', 'reply_to')
-    readonly_fields = ('created_at', 'updated_at')
+    list_display = (
+        "site",
+        "from_name",
+        "from_email",
+        "reply_to",
+        "updated_at",
+    )
+    list_select_related = ("site",)
+    search_fields = ("site__domain", "from_name", "from_email", "reply_to")
+    readonly_fields = ("created_at", "updated_at")
     fieldsets = (
-        (None, {
-            'fields': ('site',)
-        }),
-        ('Email Settings', {
-            'fields': (
-                'api_key',
-                ('from_name', 'from_email'),
-                'reply_to'
-            ),
-            'description': 'Configure the email settings. The From field in emails will appear as "From Name <from@email.com>"'
-        }),
-        ('Timestamps', {
-            'fields': ('created_at', 'updated_at'),
-            'classes': ('collapse',)
-        })
+        (None, {"fields": ("site",)}),
+        (
+            "Email Settings",
+            {
+                "fields": ("api_key", ("from_name", "from_email"), "reply_to"),
+                "description": 'Configure the email settings. The From field in emails will appear as "From Name <from@email.com>"',
+            },
+        ),
+        (
+            "Timestamps",
+            {"fields": ("created_at", "updated_at"), "classes": ("collapse",)},
+        ),
     )
 
     def get_queryset(self, request):
-        return super().get_queryset(request).select_related('site')
+        return super().get_queryset(request).select_related("site")
 
     def formfield_for_foreignkey(self, db_field, request, **kwargs):
         if db_field.name == "site":
-            kwargs["queryset"] = Site.objects.all().order_by('domain')
+            kwargs["queryset"] = Site.objects.all().order_by("domain")
         return super().formfield_for_foreignkey(db_field, request, **kwargs)