Text Completion/Raw Input support?

[oofdere]

Looking at the docs, I couldn't see any clear way to use raw text completions with the models. It doesn't seem to be available on the server either.

[EricLBuehler]

@oofdere on the server and Python APIs, you can use the completions API (modelled after or OpenAI compatible) to do this. I will add support for raw text completions to the Rust API.