fix final step

certificates/models.py

@@ -1,6 +1,7 @@
 from django.db import models
 from django.contrib.auth import get_user_model
 from common.models import BaseModel
+from _helpers.utils import jalali_converter2
 
 User = get_user_model()
 
@@ -35,4 +36,7 @@ class CertificateInstance(BaseModel):
     def __str__(self):
         return f"گواهی {self.process_instance.code}"
 
+    def jissued_at(self):
+        return jalali_converter2(self.issued_at)
+