feat(openai): added support for o1 reasoning models

[KeganHollern]

Summary

1. Fixing a bug with systemRoleSupported for the OpenAI endpoint.
2. Now using max_completion_tokens over max_tokens when querying chat_completions endpoint.

The bugfix is necessary as o1-preview and o1-mini models do not support "system" message types.
The token configuration change was necessary as o1-preview and o1-mini no longer support the, now deprecated, max_tokens field.

Considerations

I added a new endpoint configuration field called useCompletionTokens and defaulted it to true.
This would have the effect of changing the default chat_completions call to use max_completion_tokens over max_tokens.
There may be unintended consequences for users, as this could increase their overall token usage per query (as the default would change).
It may be prudent to start with this field set to false, and later switch to true as part of a planned deprecate of max_tokens all together.

Another consideration is that my change for system messages will leave a "role": "user", "content": "" entry. One thing we may want is to drop the system message entirely if content is blank and system messages are not supported.

Reference

For those wanting to introduce o1 reasoning models based on this PR (future readers), here is an example implementation of o1-mini:

{
      "name": "o1-mini",
      "displayName": "o1 mini test",
      "multimodal": false,
      "description": "ChatGPT o1-mini",
      "systemRoleSupported": false,
      "parameters": {
        "max_new_tokens": 2048,
      },
      "endpoints" : [{
        "type": "openai",
      }]
}

[evalstate]

this is cool - i had a crack at this a while ago ( #1540 (comment) ) at which point streaming wasn't supported so i had to do some extra messing around (i capture token usage too).

[nsarrazin]

Hi! Thanks for the contrib. I made a couple changes:

• Added an example in the doc
• Made the parameter false by default (like you said, probably better to not change the default behaviour for now)
• Fixed the linting

Overall this looks great, tried it locally and it seems to work well. Will merge once the checks are done. 🚀