feat(image): support `response_type` in the OpenAI API request (#2347)

* Change response_format type to string to match OpenAI Spec

Signed-off-by: prajwal <prajwalnayak7@gmail.com>

* updated response_type type to interface

Signed-off-by: prajwal <prajwalnayak7@gmail.com>

* feat: correctly parse generic struct

Signed-off-by: mudler <mudler@localai.io>

* add tests

Signed-off-by: mudler <mudler@localai.io>

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Signed-off-by: prajwal <prajwalnayak7@gmail.com>
Signed-off-by: mudler <mudler@localai.io>
Co-authored-by: Ettore Di Giacinto <mudler@users.noreply.github.com>
Co-authored-by: mudler <mudler@localai.io>