pub fn post(
url: &str,
content_type: &str,
user_agent: &str,
body: &str,
max_bytes: usize,
timeout_secs: u64,
) -> Result<FetchedDoc, String>Expand description
POST body to url (SSRF-guarded, bounded, redirects not followed).
Needed for JSON-RPC style endpoints — e.g. YouTube’s InnerTube player
API, whose caption URLs are server-fetchable (unlike the watch-page ones).
user_agent is explicit because some APIs validate it against the declared
client.