Function parse_headers_file 

pub fn parse_headers_file(path: &Path) -> Result<Vec<(String, String)>, String>

Parse headers from a file supporting both simple and curl config formats

Supported formats:

• Simple: Header-Name: Header-Value
• Curl config: header = Name: Value or -H "Name: Value"
• Comments: Lines starting with #
• Blank lines are ignored

Both formats can be mixed in the same file.