[Example] Use `serde` and `schemars` to write structure output

[cptrodgers]

Hi @64bit , your lib is awesome. I'm using it in my side project and it works perfectly.

I found that the structure output can be improved by use serde and schemars to make code easy to maintain like my PR #301 . I hope the PR works for you and community.

Btw, I think we can write the utility function like client.complete_structure_output<T>(...) and then user can just insert their rust struct and no need to worry about manual writing schema.
Assumtption code:

#[derive(Debug, Serialize, Deserialize, JsonSchema)]
#[serde(deny_unknown_fields)]
pub struct Step {
    pub output: String,
    pub explanation: String,
}

#[derive(Debug, Serialize, Deserialize, JsonSchema)]
#[serde(deny_unknown_fields)]
pub struct MathReasoningResponse {
    pub final_answer: String,
    pub steps: Vec<Step>,
}

let request = CreateChatCompletionRequestArgs::default()
    .max_tokens(512u32)
    .model("gpt-4o-mini")
    .messages(messages)
    .complete_structure_output<MathReasoningResponse>()
    .build()?;

let client = Client::new();
let response = client.chat().create(request).await?;

Thanks

[cptrodgers]

I would love to make another to add a PR to addcomplete_structure_output fn in the library if you think it's worth.

[64bit]

Thanks for a great suggestion. I'd avoid that for now to reduce maintenance burden.

I'd happily accept the example that showcases this idea without changes to library as you did in #301 , however please create it as a new example instead of updating existing one.

[cptrodgers]

Got the idea, just updated #301 to another directory.