Experimental feature proposal (Inline-Activity)

[alob-mtc]

Experimental Feature Proposal

This issue proposes an experimental feature for inline activity creation and execution.

Proposed API Usage

let future = activity_executor
    .activity()
    .max_retry(3)
    .idempotency("123")
    .run(json!({}), async |ctx: ActivityContext, payload: serde_json::Value| -> ActivityHandlerResult {
        let fx_quote = client
            .get_fx_quote(FxQuoteRequest {
                source_currency: payload.source_currency.string(),
                target_currency: payload.target_currency.string(),
                amount: payload.amount,
            })
            .await
            .map_err(|e| ActivityError::Retry(e.to_string()))?;

        let fx_quote_reference = fx_quote.reference.clone();
        let fx_quote = client
            .execute_fx(ExecuteFxRequest {
                quote_reference: fx_quote.reference.clone(),
            })
            .await
            .map_err(|e| ActivityError::Retry(e.to_string()))?;

        Ok(json!({
            "amount": fx_quote.target.amount,
            "reference": fx_quote_reference,
        }))
    })
    .await;

match future.get_result().await.unwrap(); {
    Ok() => {}
    _ => {}
}