fix date in payment and imporove contract page.

invoices/models.py

@@ -7,6 +7,7 @@ from decimal import Decimal
 from django.utils import timezone
 from django.core.validators import MinValueValidator
 from django.conf import settings
+from _helpers.utils import jalali_converter2
 
 User = get_user_model()
 
@@ -372,3 +373,6 @@ class Payment(BaseModel):
         except Exception:
             pass
         return result
+
+    def jpayment_date(self):
+        return jalali_converter2(self.payment_date)