Function content_type_charset_with_key

pub fn content_type_charset_with_key(
    content_type: &str,
    charset_with_key: &str,
) -> String

Combines a content type and a charset into a single formatted string.

• content_type: The content type (e.g., "text/html").
• charset: The character set (e.g., "charset=utf-8").
• Returns: A format string.