Resurrect method doesn't remove expired_at for deleted_dids
Motivation
----------
The resurrect method doesn't remove the expired_at when a DID is resurrected which triggers the immediate deletion of the resurrected DID

diff --git a/lib/rucio/core/did.py b/lib/rucio/core/did.py
index 68a065329..a38e4a63b 100644
--- a/lib/rucio/core/did.py
+++ b/lib/rucio/core/did.py
@@ -1591,6 +1591,8 @@ def resurrect(dids, session=None):
         #    raise exception.UnsupportedOperation("File '%(scope)s:%(name)s' cannot be resurrected" % did)
 
         kargs = del_did.to_dict()
+        if kargs['expired_at']:
+            kargs['expired_at'] = None
         kargs.pop("_sa_instance_state", None)
 
         session.query(models.DeletedDataIdentifier).\\
['lib/rucio/core/did.py']