Function is_transient_connection_error

tests/common/mod.rs:510–526

True when a `ureq` error is a connection-level failure that a freshly started (or briefly overloaded) server can transiently raise before it is steadily accepting requests: peer disconnected, connection refused/reset, or a bare I/O error. These are safe to retry for idempotent test requests; an HTTP status error is NOT one of these (the agent is built with `http_status_as_error(false)`, so 4xx/5xx

(err: &ureq::Error)

/// an HTTP status error is NOT one of these (the agent is built with
/// `http_status_as_error(false)`, so 4xx/5xx come back as `Ok`).
pub fn is_transient_connection_error(err: &ureq::Error) -> bool {
    match err {
        ureq::Error::ConnectionFailed => true,
        ureq::Error::Io(_) => true,
        other => {
            // Fall back to a message match so newer/renamed variants (e.g.
            // "Peer disconnected", "connection reset") still count as transient
            // without pinning to a specific ureq version's enum shape.
            let text = other.to_string().to_ascii_lowercase();
            text.contains("peer disconnected")
                || text.contains("connection refused")
                || text.contains("connection reset")
                || text.contains("broken pipe")
                || text.contains("timed out")
        }
    }
}

/// Issues an idempotent HTTP request, retrying transient connection-level
/// errors (the server racing its own readiness under parallel load) with a