Function fetch_chunk

crates/openshell-supervisor-network/src/policy_local.rs:929–939

One gateway call: list the sandbox's draft chunks and find the matching id. Returns `Ok(None)` only when the gateway responded successfully but no chunk in this sandbox matches.

(
    session: &LookupSession<'_>,
    chunk_id: &str,
)

/// id. Returns `Ok(None)` only when the gateway responded successfully but
/// no chunk in this sandbox matches.
async fn fetch_chunk(
    session: &LookupSession<'_>,
    chunk_id: &str,
) -> std::result::Result<Option<PolicyChunk>, (u16, serde_json::Value)> {
    let chunks = session
        .client
        .get_draft_policy(session.sandbox_name, "")
        .await
        .map_err(|e| (502, error_payload("gateway_lookup_failed", e.to_string())))?;
    Ok(chunks.into_iter().find(|c| c.id == chunk_id))
}

fn proposal_chunks_from_body(body: &[u8]) -> std::result::Result<Vec<PolicyChunk>, String> {
    let request: ProposalRequest = serde_json::from_slice(body).map_err(|e| e.to_string())?;