fix(migrations): certificate migrate err

Author: duanhongyi

rootfs/api/migrations/0013_migration_permissions_and_certificates.py

@@ -18,10 +18,13 @@ def migration_permission(apps, schema_editor):
 def migration_certificate(apps, schema_editor):
     for domain in Domain.objects.all():
         if domain.certificate:
-            certificate = domain.certificate
-            certificate.pk = None
-            certificate.app = domain.app
-            certificate.save()
+            certificate = Certificate.objects.filter(
+                app=domain.app, name=domain.certificate.name).first()
+            if not certificate:
+                certificate = domain.certificate
+                certificate.pk = None
+                certificate.app = domain.app
+                certificate.save()
             domain.certificate = certificate
             domain.save()
     Certificate.objects.filter(app=None).delete()