Return the NID of the authentication method used by a cipher suite.
Declared in <openssl/ssl.h>
<openssl/ssl.h>
int SSL_CIPHER_get_auth_nid(SSL_CIPHER const* c);
Authentication NID (for example NID_auth_ecdsa), NID_auth_any for TLSv1.3 suites, or NID_undef if none.