Convert to iso format after creating a dict of the whole memory (#1174)

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-->

## Summary by CodeRabbit

- **New Features**
	- Enhanced event data handling with ISO format strings for dates.
- Introduced new classes for managing workflow-related memory sources
and their creation.

- **Bug Fixes**
	- Improved serialization of event data within the Memory model.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

backend/models/memory.py

@@ -195,8 +195,8 @@ def get_transcript(self, include_timestamps: bool) -> str:
         return TranscriptSegment.segments_as_string(self.transcript_segments, include_timestamps=include_timestamps)
 
     def as_dict_cleaned_dates(self):
-        self.structured.events = [event.as_dict_cleaned_dates() for event in self.structured.events]
         memory_dict = self.dict()
+        memory_dict['structured']['events'] = [event['start'].isoformat() for event in memory_dict['structured']['events']]
         memory_dict['created_at'] = memory_dict['created_at'].isoformat()
         memory_dict['started_at'] = memory_dict['started_at'].isoformat() if memory_dict['started_at'] else None
         memory_dict['finished_at'] = memory_dict['finished_at'].isoformat() if memory_dict['finished_at'] else None