stdkoehler

Union produces anyOf instead of oneOf for OpenAPI generation

3

### First Check - [X] I added a very descriptive title to this issue. - [X] I used the GitHub search to find a similar issue and didn't find it....

**Description** Many of the parameters available for the custom models are not available for the real OpenAI model (e.g. top_k but almost all other parameters as well), Libraries that are...