Use JSONDataEncoder to encode task createdDate

This commit modifies the MCPServer to encode the `createdDate` of tasks using
`datetime` which is natively supported by our JSONDataEncoder. The conversion
to the METS-compliant format now occurs during the decoding process on the
client side. This change ensures consistent use of RFC 3339 format across all
communications.

src/MCPClient/lib/client/gearman.py

@@ -1,6 +1,7 @@
 import functools
 import logging
 import multiprocessing
+from datetime import datetime
 
 import gearman
 from client import metrics
@@ -66,9 +67,16 @@ def _prepare_jobs(task_name, gearman_job):
 
         jobs = []
         for task_uuid, task_data in tasks.items():
+            # We use ISO 8601 in our wire format but replace the `T` separator
+            # with a space for METS compatibility in client scripts.
+            created_date = datetime.fromisoformat(task_data["createdDate"]).isoformat(
+                " "
+            )
             arguments = str(task_data["arguments"])
             arguments = replace_task_arguments(
-                arguments, task_uuid, task_data.get("createdDate")
+                arguments,
+                task_uuid,
+                created_date,
             )
             arguments = parse_command_line(arguments)
 

src/MCPServer/lib/server/tasks/backends/gearman_backend.py

@@ -190,7 +190,7 @@ def failed(self):
     def serialize_task(self, task):
         return {
             "uuid": str(task.uuid),
-            "createdDate": task.start_timestamp.isoformat(" "),
+            "createdDate": task.start_timestamp,
             "arguments": task.arguments,
             "wants_output": task.wants_output,
         }

tests/MCPServer/test_gearman.py

@@ -39,7 +39,7 @@ def format_gearman_request(tasks):
         task_uuid = str(task.uuid)
         request["tasks"][task_uuid] = {
             "uuid": task_uuid,
-            "createdDate": task.start_timestamp.isoformat(" "),
+            "createdDate": task.start_timestamp,
             "arguments": task.arguments,
             "wants_output": task.wants_output,
         }