[AI Bundle] Provide an easy way to add input/output processor to an agent via config

[VincentLanglet]

Looking at https://github.com/symfony/ai/blob/main/src/ai-bundle/config/options.php
and https://github.com/symfony/ai/blob/main/src/ai-bundle/src/AiBundle.php

I don't see an easy way to add an input/output processor to a platform or an agent.
They currently only added with custom config like

• structured_output
• system_prompt
• ...

So it's not easy to add a custom input/output processor. Am I wrong ?

[VincentLanglet]

I'm open to do the PR but I'd like your opinion on how the config should be modified @OskarStark @chr-hertel :)

[chr-hertel]

I think two ways would be great:

1. adding it via config on the agent - especially if there are third party services that you want as a input/output processor
2. adding it on your own code with an attribute #[AsOutputProcessor(agent: 'xyz')

makes sense?

[OskarStark]

Is this done?

[VincentLanglet]

#352 is not merged yet

[chr-hertel]

Implemented with #352