some fields validation and model cleaning

preinfo/models.py

@@ -1,8 +1,12 @@
 from django.db import models
 
+from common.fields import ContainerNumberField
+from containers.models import Container
+
+
 # Create your models here.
 class Preinfo(models.Model):
-    container_number = models.CharField(
+    container_number = ContainerNumberField(
         max_length=11,
     )
     container_type = models.ForeignKey(
@@ -33,3 +37,7 @@ class Preinfo(models.Model):
     )
     deleted_on = models.DateTimeField(null=True, blank=True)
     received = models.BooleanField(default=False, null=False)
+
+    def clean(self):
+        if Container.objects.filter(number=self.container_number, expedited=False).exists():
+            raise ValueError(f'Container with number {self.container_number} is at the depot.')