Function decode_body 

pub(crate) fn decode_body<T: DeserializeOwned>(
    headers: &HeaderMap,
    body: &[u8],
) -> Result<T, ApiError>

Decode a request body based on its Content-Type, matched by media-type essence.

• application/octet-stream: VBS (versioned binary), what Request::body_binary sends, and what production peer-catchup / submit-transactions clients use.
• application/json: serde_json.