Not clear error message when agent name is not valid (0.2 branch).

[giorgossideris]

What feature would you like to be added?

This issue refers to the 0.2 branch.

The message when an agent name is not valid (based on the OpenAI's expected pattern) should be clearer (this problem is fixed in the main branch here).

The message right now is: BadRequestError: Error code: 400 - {'error': {'message': "Invalid 'messages[1].name': string does not match pattern. Expected a string that matches the pattern '^[a-zA-Z0-9_-]+$'.", 'type': 'invalid_request_error', 'param': 'messages[1].name', 'code': 'invalid_value'}}

Why is this needed?

It will be easier to identify the problem.