Allow disabling Bearer auth for OpenAi models #2218
Description
At Netflix we have a model abstraction that uses the OpenAi REST API.
Because this is an internal service, we use a different auth mechanism, and adding an Authorization header to the request is not allowed.
I'm integrating Spring AI with this internal model abstraction and need a way to disable adding the Authorization header.
I created a simple PR with a possible fix based on the ApiKey interface, but alternatively, a property would work as well. The PR assumes that a user brings their own beans for the models, overriding the beans from OpenAiAutoConfiguration.
As a side note, I noticed that while OpenAiApi uses the ApiKey interface, both OpenAiAudioApi and OpenAiImageApi still use a String instead of the ApiKey interface. I didn't want to touch this in the PR because it's an API change, but that's probably worth aligning.