Refactor code structure; improve organization and readability across multiple files

models/brands.py

@@ -16,4 +16,10 @@ class Brand(db.Model):
     inventory: Mapped[List['Inventory']] = relationship('Inventory', back_populates='brand')
 
     def __repr__(self):
-        return f"<Brand(id={self.id}, name={repr(self.name)})>"
+        return f"<Brand(id={self.id}, name={repr(self.name)})>"
+    
+    def serialize(self):
+        return {
+            'id': self.id,
+            'name': self.name
+        }