Various updates

uncloud_vm/models.py

@@ -164,9 +164,7 @@ class VMDiskProduct(Product):
         default=VMDiskType.CEPH_SSD)
 
     def __str__(self):
-        return "{} disk for VM '{}': {}GB".format(self.disk_type,
-                                                  self.vm.name,
-                                                  self.size_in_gb)
+        return f"Disk {self.size_in_gb}GB ({self.disk_type}) for VM '{self.vm.name}'"
 
     @property
     def recurring_price(self):