Add demo models with auditlog features

- Add Post, Category, Tag models demonstrating various field types

sample_project/demo/models.py

@@ -0,0 +1,62 @@
+from django.conf import settings
+from django.db import models
+
+
+class Category(models.Model):
+    """Blog post category model for organizing content."""
+
+    name = models.CharField(max_length=50, help_text="Category name")
+
+    class Meta:
+        verbose_name = "Category"
+        verbose_name_plural = "Categories"
+        ordering = ["name"]
+
+    def __str__(self):
+        return self.name
+
+
+class Tag(models.Model):
+    """Tag model for labeling posts with keywords."""
+
+    name = models.CharField(max_length=50, help_text="Tag name")
+
+    class Meta:
+        verbose_name = "Tag"
+        verbose_name_plural = "Tags"
+        ordering = ["name"]
+
+    def __str__(self):
+        return self.name
+
+
+class Post(models.Model):
+    """Blog post model demonstrating auditlog tracking with various field types."""
+
+    author = models.ForeignKey(
+        settings.AUTH_USER_MODEL,
+        on_delete=models.SET_NULL,
+        null=True,
+        blank=True,
+        help_text="Post author",
+    )
+    category = models.ForeignKey(
+        Category,
+        on_delete=models.SET_NULL,
+        null=True,
+        blank=True,
+        help_text="Post category",
+    )
+    tags = models.ManyToManyField(Tag, blank=True, help_text="Post tags")
+    title = models.CharField(max_length=200, help_text="Post title")
+    content = models.TextField(help_text="Post content")
+    created_at = models.DateTimeField(auto_now_add=True)
+    updated_at = models.DateTimeField(auto_now=True)
+
+    class Meta:
+        verbose_name = "Post"
+        verbose_name_plural = "Posts"
+        ordering = ["-created_at"]
+
+    def __str__(self):
+        return self.title