fix: remove default temperature on all QueryTransformer implementations

[apappascs]

resolving #2243

[ilayaperumalg]

@apappascs Thanks for the PR!

[ilayaperumalg]

@ThomasVitale Is there any specific reason why we had the temperature set here?

[ThomasVitale]

It's recommended to set the temperature to a low value when performing query transformations to ensure more accurate results that will improve the retrieval quality. After removing this, it will be up to the developer to set the temperature on the ChatClient.Builder when instantiating a QueryTransformer. We need to specify that in the documentation as a pre-requisite to use a query transformer, because the typical default temperature is too high and will affect the retrieval quality.

All these modular RAG APIs and implementations are still in an experimental state. This is good input to perhaps review some design choices and improve the APIs, ensuring both good out-of-the-box experience, but also flexibility.

Side note:
This is not the first place where we see problems with the OpenAI reasoning models behaving differently. It feels like something that should be handled at the ChatModel API level so to have a general handling of those differences in one place, rather than addressing incompatibilities wherever they occur.

[apappascs]

Thank you for the feedback, @ThomasVitale. I have updated the documentation based on your comment.

[markpollack]

ok to merge

[ilayaperumalg]

@apappascs Thanks for the PR. Squashed, rebased and merged as 59fbd9e