Function execute_request 

pub fn execute_request(
    method: Method,
    url: &str,
    headers: HeaderMap,
    body: HttpBody,
) -> Result<HttpResponse>

Send a blocking HTTP request and read the response into HttpResponse.

This helper is deliberately protocol-agnostic: the caller composes the URL, headers, and body, then hands them in. REST-aware decisions (Accept defaults, bearer-token shaping, JSON serialisation, multipart assembly) live in rest::runner::execute_rest_request; future non-REST backends layer their own conventions on top of this primitive.