fix(SECURITY): return error on failed DANE verification

and add raw cert caching in DANE verificator

examples/main.rs

@@ -149,8 +149,7 @@ impl SelfsignedCertVerifier for CertVerifier {
                         CertFingerprint::new_sha256(cert)
                     }
                     Err(e) => {
-                        // some other problem (e.g. DNS server rejected the request),
-                        // we shouldn't continue
+                        // cert not matched, DNS server rejected request, etc.
                         eprintln!("DANE verification failed: {:?}", e);
                         return Err(e);
                     }