feat: Refactor rides app with unique constraints, mixins, and enhanced documentation

- Added migration to convert unique_together constraints to UniqueConstraint for RideModel.
- Introduced RideFormMixin for handling entity suggestions in ride forms.
- Created comprehensive code standards documentation outlining formatting, docstring requirements, complexity guidelines, and testing requirements.
- Established error handling guidelines with a structured exception hierarchy and best practices for API and view error handling.
- Documented view pattern guidelines, emphasizing the use of CBVs, FBVs, and ViewSets with examples.
- Implemented a benchmarking script for query performance analysis and optimization.
- Developed security documentation detailing measures, configurations, and a security checklist.
- Compiled a database optimization guide covering indexing strategies, query optimization patterns, and computed fields.

backend/apps/accounts/tests/test_model_constraints.py

@@ -0,0 +1,101 @@
+"""
+Tests for model constraints and validators in the accounts app.
+
+These tests verify that:
+1. CheckConstraints raise appropriate errors
+2. Validators work correctly
+3. Business rules are enforced at the model level
+"""
+
+from django.test import TestCase
+from django.db import IntegrityError
+from django.core.exceptions import ValidationError
+from django.utils import timezone
+
+from apps.accounts.models import User
+
+
+class UserConstraintTests(TestCase):
+    """Tests for User model constraints."""
+
+    def test_banned_user_without_ban_date_raises_error(self):
+        """Verify banned users must have a ban_date set."""
+        user = User(
+            username="testuser",
+            email="test@example.com",
+            is_banned=True,
+            ban_date=None,  # This should violate the constraint
+        )
+
+        # The constraint should be enforced at database level
+        with self.assertRaises(IntegrityError):
+            user.save()
+
+    def test_banned_user_with_ban_date_saves_successfully(self):
+        """Verify banned users with ban_date save successfully."""
+        user = User.objects.create_user(
+            username="testuser2",
+            email="test2@example.com",
+            password="testpass123",
+            is_banned=True,
+            ban_date=timezone.now(),
+        )
+        self.assertIsNotNone(user.pk)
+        self.assertTrue(user.is_banned)
+        self.assertIsNotNone(user.ban_date)
+
+    def test_non_banned_user_without_ban_date_saves_successfully(self):
+        """Verify non-banned users can be saved without ban_date."""
+        user = User.objects.create_user(
+            username="testuser3",
+            email="test3@example.com",
+            password="testpass123",
+            is_banned=False,
+            ban_date=None,
+        )
+        self.assertIsNotNone(user.pk)
+        self.assertFalse(user.is_banned)
+
+    def test_user_id_is_auto_generated(self):
+        """Verify user_id is automatically generated on save."""
+        user = User.objects.create_user(
+            username="testuser4",
+            email="test4@example.com",
+            password="testpass123",
+        )
+        self.assertIsNotNone(user.user_id)
+        self.assertTrue(len(user.user_id) >= 4)
+
+    def test_user_id_is_unique(self):
+        """Verify user_id is unique across users."""
+        user1 = User.objects.create_user(
+            username="testuser5",
+            email="test5@example.com",
+            password="testpass123",
+        )
+        user2 = User.objects.create_user(
+            username="testuser6",
+            email="test6@example.com",
+            password="testpass123",
+        )
+        self.assertNotEqual(user1.user_id, user2.user_id)
+
+
+class UserIndexTests(TestCase):
+    """Tests for User model indexes."""
+
+    def test_is_banned_field_is_indexed(self):
+        """Verify is_banned field has db_index=True."""
+        field = User._meta.get_field('is_banned')
+        self.assertTrue(field.db_index)
+
+    def test_role_field_is_indexed(self):
+        """Verify role field has db_index=True."""
+        field = User._meta.get_field('role')
+        self.assertTrue(field.db_index)
+
+    def test_composite_index_exists(self):
+        """Verify composite index on (is_banned, role) exists."""
+        indexes = User._meta.indexes
+        index_names = [idx.name for idx in indexes]
+        self.assertIn('accounts_user_banned_role_idx', index_names)