Add response interceptor

[sashirestela]

Discussed in #86

^{Originally posted by the-gigi January 2, 2025}
The idea is similar to the request interceptor, which allows users to register a hook that can modify the request just before it is sent.

The motivation is a bug in the OpenAI compatibility of the Gemini API, which can be worked around by modifying the response coming back from Gemini.

See https://discuss.ai.google.dev/t/openai-compatibility-bug-in-response-object/58484

@sashirestela you mentioned in this simple-openai issue that I should open a cleverclient issue, but them said that it would be more difficult:
sashirestela/simple-openai#248 (comment)

So, instead of opening an issue I'm starting this discussion to understand the difficulty.

[the-gigi]

This is great. Thanks @sashirestela

[the-gigi]

@sashirestela I'm happy to report that this works like a charm. All our integration tests now work with Gemini.

[sashirestela]

@the-gigi so, are you in a better position to retake this sashirestela/simple-openai#248?

[the-gigi]

@sashirestela Yes. I need to find the time.