Add comment system with models, forms, and UI integration for lessons

courses/models.py

@@ -41,4 +41,20 @@ class Lesson(models.Model):
             self.content = self.content.replace('?>', '?>')
 
     def __str__(self):
-        return self.name
+        return self.name
+
+
+class Comment(models.Model):
+    lesson = models.ForeignKey(Lesson, on_delete=models.CASCADE, related_name='comments')
+    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name='lesson_comments')
+    content = models.TextField()
+    parent = models.ForeignKey('self', on_delete=models.CASCADE, null=True, blank=True, related_name='replies')
+    created_at = models.DateTimeField(auto_now_add=True)
+    updated_at = models.DateTimeField(auto_now=True)
+    is_active = models.BooleanField(default=True)
+
+    class Meta:
+        ordering = ("created_at",)
+
+    def __str__(self):
+        return f"Comment by {self.user} on {self.lesson}"