Make API endpoint URL configurable in OpenAiClient

[mysticfall]

What is the problem this feature would solve?

Several LLM backends, like OpenRouter or Text Generation WebUI, provide an OpenAI-compatible HTTP API.

However, the current implementation of OpenClient in the ai package doesn't allow the user to change the default endpoint URL, which is hardcoded as https://api.openai.com/v1.

It could be a major limitation for many users since OpenAI only provides their own proprietary LLM models, while many different base models and finetunes exist that may provide better features for them.

What is the feature you are proposing to solve the problem?

Make API endpoint URL configurable in OpenAiClient.

What alternatives have you considered?

Add a baseURL or url argument to the OpenAIClient.make function.