Function curl_json 

pub fn curl_json(url: &str) -> Result<Value, Box<dyn Error + Send + Sync>>

What: Fetch JSON from a URL using curl and parse into serde_json::Value.

Inputs:

• url: HTTP(S) URL to request

Output:

• Ok(Value) on success; Err if curl fails or the response is not valid JSON

Errors

• Returns Err when curl command execution fails (I/O error or curl not found)
• Returns Err when curl exits with non-zero status (network errors, HTTP errors, timeouts)
• Returns Err when response body cannot be decoded as UTF-8
• Returns Err when response body cannot be parsed as JSON

Details:

• Executes curl with appropriate flags and parses the UTF-8 body with serde_json.
• On Windows, uses -k flag to skip SSL certificate verification.
• Provides user-friendly error messages for common curl failure cases.
• For HTTP errors, includes the actual status code in the error message when available.