V9.0 fix get transformations files count

[chaen]

Avoid this crash

2025-04-16T08:01:03,128907Z Transformation/TransformationManager ERROR: Exception while executing handler action
Traceback (most recent call last):
  File "/opt/dirac/versions/v12.0.0a17-1744604884/Linux-x86_64/lib/python3.11/site-packages/DIRAC/Core/DISET/private/Service.py", line 554, in _executeAction
    response = handlerObj._rh_executeAction(proposalTuple)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/dirac/versions/v12.0.0a17-1744604884/Linux-x86_64/lib/python3.11/site-packages/DIRAC/Core/DISET/RequestHandler.py", line 144, in _rh_executeAction
    result = self.__trPool.send(self.__trid, retVal)  # this will delete the value from the S_OK(value)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/dirac/versions/v12.0.0a17-1744604884/Linux-x86_64/lib/python3.11/site-packages/DIRAC/Core/DISET/private/TransportPool.py", line 109, in send
    return transport.sendData(msg)
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/dirac/versions/v12.0.0a17-1744604884/Linux-x86_64/lib/python3.11/site-packages/DIRAC/Core/DISET/private/Transports/BaseTransport.py", line 168, in sendData
    sCodedData = MixedEncode.encode(uData)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/dirac/versions/v12.0.0a17-1744604884/Linux-x86_64/lib/python3.11/site-packages/DIRAC/Core/Utilities/MixedEncode.py", line 16, in encode
    return JEncode.encode(inData)
           ^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/dirac/versions/v12.0.0a17-1744604884/Linux-x86_64/lib/python3.11/site-packages/DIRAC/Core/Utilities/JEncode.py", line 186, in encode
    return json.dumps(inData, cls=DJSONEncoder)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/dirac/versions/v12.0.0a17-1744604884/Linux-x86_64/lib/python3.11/json/__init__.py", line 238, in dumps
    **kw).encode(obj)
          ^^^^^^^^^^^
  File "/opt/dirac/versions/v12.0.0a17-1744604884/Linux-x86_64/lib/python3.11/json/encoder.py", line 200, in encode
    chunks = self.iterencode(o, _one_shot=True)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/dirac/versions/v12.0.0a17-1744604884/Linux-x86_64/lib/python3.11/json/encoder.py", line 258, in iterencode
    return _iterencode(o, 0)
           ^^^^^^^^^^^^^^^^^
TypeError: keys must be str, int, float, bool or None, not datetime.date

BEGINRELEASENOTES
*TS
FIX: Explicitly cast to string when returning dates

ENDRELEASENOTES