add translations

election/models.py

@@ -130,6 +130,16 @@ class Role(OrderedModel):
 
     order_with_respect_to = "election"
 
+    class Meta(OrderedModel.Meta):
+        constraints = [
+            models.UniqueConstraint(
+                fields=["title", "election"],
+                name="title_election_unique_constraint",
+                violation_error_message=_("This role already exists for this election"),
+                violation_error_code="invalid",
+            )
+        ]
+
     def __str__(self):
         return f"{self.title} - {self.election.title}"