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/rides/mixins.py

@@ -0,0 +1,49 @@
+"""
+Mixins for ride views.
+
+This module contains mixins that provide reusable functionality
+for ride-related views, reducing code duplication.
+"""
+
+from typing import Any, Dict
+
+from django.contrib import messages
+
+from apps.rides.services import RideService
+
+
+class RideFormMixin:
+    """
+    Mixin for handling ride form submissions with entity suggestions.
+
+    Provides common functionality for RideCreateView and RideUpdateView
+    to handle new manufacturer, designer, and ride model suggestions.
+    """
+
+    def handle_entity_suggestions(self, form) -> Dict[str, Any]:
+        """
+        Process new entity suggestions from form.
+
+        Creates moderation submissions for any new manufacturers,
+        designers, or ride models that were suggested but don't
+        exist in the system.
+
+        Args:
+            form: Validated form instance with cleaned_data
+
+        Returns:
+            Dictionary with submission results from RideService
+        """
+        result = RideService.handle_new_entity_suggestions(
+            form_data=form.cleaned_data,
+            submitter=self.request.user
+        )
+
+        if result['total_submissions'] > 0:
+            messages.info(
+                self.request,
+                f"Created {result['total_submissions']} moderation submission(s) "
+                "for new entities"
+            )
+
+        return result