[OTel]: Spans produced by `spin_sdk::key_value::Store::set` don't have a parent assigned

Spans produced as part of using the key-value store set function, don't have a parent assigned. This results in having two independent traces from a single HTTP API invocation

I've tested other actions in the context of key-value store (such as exists and `get) which are all represented correctly:

Versions

• spin CLI: spin 2.5.1 (cba6773 2024-05-14)
• spin-sdk crate: 3.0.1

Repro

See the following pseudo code for reproducing the behavior:

use spin_sdk::http::{IntoResponse, Request, Response};
use spin_sdk::http_component;
use spin_sdk::key_value::Store;

/// A simple Spin HTTP component.
#[http_component]
fn handle_api(req: Request) -> anyhow::Result<impl IntoResponse> {
    println!("Handling request to {:?}", req.header("spin-full-url"));
    let store = Store::open_default()?;
    let exists = store.exists("foo")?;
    if !exists {
        return Ok(Response::new(404, ()));
    }

    let Some(value) = store.get("foo")? else {
        return Ok(Response::new(204, ()));
    };

    store.set("bar", b"baz")?;

    Ok(Response::builder()
        .status(200)
        .header("content-type", "text/plain")
        .body(value)
        .build())
}

Start at the Rust SDK implementation of spin_sdk::key_value::Store::set and compare its tracing behavior with the exists and get operations described in the report. Reproduce the HTTP component example with OpenTelemetry enabled, then identify the relevant tracing test or add coverage showing that set's span belongs to the request trace.