`create_tool_def` requires OpenAI key

[jcheng5]

Either we should document this limitation, or make it possible to use other providers.

[hadley]

I briefly explored making this generic across providers but it was a bit harder than I thought. We might need to make #112 work and add some way to reset turns so that the user could provide any existing chat instance and create_tool_def() would clone and reset it.

[jcheng5]

One more option, we could deploy a public Shiny app that lets you paste in a function and you get the ToolDef.

[hadley]

Or a plumber API

[vorpalvorpal]

Maybe I'm misunderstanding the issue, but I made an identical function that replaced the call to chat_openai with chat_claude. Couldn't there simply be another parameter that allows the user to select the chat function? If you wanted to get fancy you could have some sort of dictionary that looked up the appropriate chat function based on the model provided. Possibly there could be some environment variable that sets the default chat function and possibly also the default model, and then this and other functions in elmer could read that.