added model level constraints

action/models.py

@@ -1,4 +1,5 @@
 from django.db import models, connection
+from django.db.models import Max
 from user.models import User, Institution
 from django.core.exceptions import ValidationError
 
@@ -23,13 +24,31 @@ class State(models.Model):
 
 class StateDefinition(models.Model):
     institution = models.ForeignKey(Institution, on_delete=models.CASCADE)
-    order = models.AutoField(primary_key=True)
+
+    order = models.PositiveIntegerField(default=0)
     state = models.CharField(max_length=50)
 
     class Meta:
+        ordering = ['order']
         constraints = [
             models.UniqueConstraint(fields=['institution', 'state'], name='unique_institution_state')
         ]
 
+    def save(self, *args, **kwargs):
+        if not self.pk:
+            # set the order to be last
+            max_order = StateDefinition.objects.filter(institution=self.institution).aggregate(Max('order'))['order__max']
+            self.order = (max_order or 0) + 1
+        super().save(*args, **kwargs)
+
+    
+    def delete(self, *args, **kwargs):
+        institution = self.institution
+        order = self.order
+        super().delete(*args, **kwargs)
+        # Adjust the order of other instances
+        StateDefinition.objects.filter(institution=institution, order__gt=order).update(order=models.F('order') - 1)
+
+
     def __str__(self):
         return f"{self.institution.name} - {self.state}"