DateTime stamp format issues when using mixed A2A language implementations (python + Java)

### What happened?

When using a python based Agent which is fronted with a Java based orchestrator, there is a conflict with datetime format pattern.
Issues:
When sending a message from the Java orchestrator to the python agent and getting response, the unmarshall of the response throws an error about the datetime format. Java code expects a "yyyy-MM-dd'T'HH:mm:ss.SSSSSS" format while the python back end sent date time in "yyyy-MM-dd'T'HH:mm:ss.SSSSSSSSSXX" format.
Workaround:
Changed the python A2A library to send it in the Java expected format.

### Relevant log output

```shell
Failed to send message: com.fasterxml.jackson.databind.exc.InvalidFormatException: Cannot deserialize value of type `java.time.LocalDateTime` from String "2025-07-02T18:43:53.974294+00:00"
```

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