[WEB-2945] chore: handled the unique state name validation

apiserver/plane/app/views/state/base.py

@@ -1,6 +1,9 @@
 # Python imports
 from itertools import groupby
 
+# Django imports
+from django.db.utils import IntegrityError
+
 # Third party imports
 from rest_framework.response import Response
 from rest_framework import status
@@ -37,11 +40,19 @@ def get_queryset(self):
     @invalidate_cache(path="workspaces/:slug/states/", url_params=True, user=False)
     @allow_permission([ROLE.ADMIN])
     def create(self, request, slug, project_id):
-        serializer = StateSerializer(data=request.data)
-        if serializer.is_valid():
-            serializer.save(project_id=project_id)
-            return Response(serializer.data, status=status.HTTP_200_OK)
-        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
+        try:
+            serializer = StateSerializer(data=request.data)
+            if serializer.is_valid():
+                serializer.save(project_id=project_id)
+                return Response(serializer.data, status=status.HTTP_200_OK)
+            return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
+        except IntegrityError as e:
+            if "already exists" in str(e):
+                return Response(
+                    {"name": "The state name is already taken"},
+                    status=status.HTTP_400_BAD_REQUEST,
+                )
+
 
     @allow_permission([ROLE.ADMIN, ROLE.MEMBER, ROLE.GUEST])
     def list(self, request, slug, project_id):