函数 verify_server_name 

pub fn verify_server_name(
    cert: &ParsedCertificate<'_>,
    server_name: &ServerName<'_>,
) -> Result<(), Error>

验证 the end_entity has an alternative name matching the server_name。

Note: this only verifies the 名并 should be 用 in conjunction with more verification like verify_server_cert_signed_by_trust_anchor