Function validate_content_type 

pub fn validate_content_type(header_value: &str, expected_base: &str) -> bool

Validates a Content-Type header value against an expected EST media type.

Per RFC 5967 §2 and RFC 7030 §4, Content-Type headers may include optional parameters (charset, smime-type, boundary). This function matches the base media type case-insensitively and tolerates optional parameters.

Examples

assert!(validate_content_type("application/pkcs10", "application/pkcs10"));
assert!(validate_content_type("application/pkcs10; charset=utf-8", "application/pkcs10"));
assert!(validate_content_type("Application/PKCS10", "application/pkcs10"));
assert!(!validate_content_type("text/plain", "application/pkcs10"));