Add Prompts API

[Stephen Belanger (Qard)]

Prompts allow you to version and manage LLM prompts centrally, with support for variable substitution and pinning to specific versions.

let prompt = client
    .prompt_builder_with_credentials(&api_key, &org_id)
    .project_name("my-project")
    .slug("greeting-prompt")
    .build()
    .await?;

// Render with variables
let result = prompt.build(Some(hashmap! {
    "name".to_string() => json!("Alice"),
}));

// Use the rendered prompt
match result.prompt {
    RenderedPrompt::Chat(messages) => {
        // Use chat messages
    }
    RenderedPrompt::Completion(text) => {
        // Use completion text
    }
}

[Ankur Goyal (ankrgyl)]

personally think we should just avoid doing this until we can fetch prompts as lingua format (or, use lingua to convert whatever we get from the API to this). I don't tink we should have prompt typespecs redundantly defined here and lingua.

[Stephen Belanger (Qard)]

I can delay until lingua is ready, if you like? I agree that if the types are likely to change then we maybe should hold off. Though would lingua be usable in a way that we could make it an internal implementation detail of this? Or would we want it exported directly as the publicly-visible types?

[Stephen Belanger (Qard)]

I've updated to use Lingua. It's using a git dependency at the moment. How should we proceed from there?

[Abhijeet Prasad (AbhiPrasad)]

we can't publish a crate with git deps, so we'll need to fix this before that happens.

[Abhijeet Prasad (AbhiPrasad)]

template_format is in the tests, but we don't actually implement this in the PR. Should we do that?

[Abhijeet Prasad (AbhiPrasad)]

Ideally we can avoid the allow(private_bounds.

[Abhijeet Prasad (AbhiPrasad)]

we should pick a better status than 200 for the error.