added model constraints

action/models.py

@@ -1,22 +1,33 @@
 from django.db import models, connection
 from user.models import User, Institution
-
-
-class StateDefinition(models.Model):
-    institution = models.ForeignKey(Institution, on_delete=models.CASCADE)
-    order = models.PositiveIntegerField()
-    state = models.CharField(max_length=255)
-
-    def __str__(self):
-        return f"{self.institution.name} - {self.state}"
+from django.core.exceptions import ValidationError
 
 class State(models.Model):
     date = models.DateTimeField(auto_now_add=True)
     institution = models.ForeignKey(Institution, on_delete=models.CASCADE)
     user = models.ForeignKey(User, on_delete=models.SET_NULL, null=True)
 
-    state = models.CharField(max_length=255)
+    state = models.CharField(max_length=50)
     snapshot_uuid = models.UUIDField()
 
+    class Meta:
+        unique_together = ('institution', 'state')
+
     def __str__(self):
         return f"{self.institution.name} - {self.state} - {self.snapshot_uuid}"
+
+class StateDefinition(models.Model):
+    institution = models.ForeignKey(Institution, on_delete=models.CASCADE)
+    order = models.AutoField(primary_key=True)
+    state = models.CharField(max_length=50)
+
+    def clean(self):
+        if not StateDefinition.objects.filter(institution=self.institution, state=self.state).exists():
+            raise ValidationError(f"The state '{self.state}' is not valid for the institution '{self.institution.name}'.")
+    
+    def save(self, *args, **kwargs):
+        self.clean()
+        super().save(*args, **kwargs)
+
+    def __str__(self):
+        return f"{self.institution.name} - {self.state}"