[Bug]: No proper documentation for A2A request in Swagger UI for `A2AFastAPIApplication`

[inesmcm26]

What happened?

The way A2AFastAPIApplication sets up its A2A request route causes FastAPI’s Swagger UI to be less usable. Because the route is defined to receive a generic Request object, there's no model defined for the request body. As a result, FastAPI doesn’t generate any documentation for the request body, and there's no way to provide or test a request body in the Swagger UI at all.

This makes it impossible to use Swagger UI to test the endpoint directly, since you can’t input the necessary data.

Current behavior:

Expected behavior after fix:

Relevant log output

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