Refactor RRSIGRdata to use base64 encoding for the signature

src/message/rdata.rs

@@ -682,7 +682,7 @@ mod resolver_query_tests {
         rrsig_rdata.set_signature_inception(1630435200);
         rrsig_rdata.set_key_tag(1234);
         rrsig_rdata.set_signer_name(DomainName::new_from_str("example.com"));
-        rrsig_rdata.set_signature(String::from("abcdefg"));
+        rrsig_rdata.set_signature(b"abcdefg".to_vec());
 
         let expected_bytes:Vec<u8> = vec![0, 1, 5, 2, 0, 0, 14, 16, 97, 46, 119, 128, 97,
         46, 119, 128, 4, 210, 7, 101, 120, 97, 109, 112, 108, 101, 3, 99, 111, 109, 0, 97, 
@@ -1053,7 +1053,7 @@ mod resolver_query_tests {
                 assert_eq!(val.get_signature_inception(), 1630435200);
                 assert_eq!(val.get_key_tag(), 1234);
                 assert_eq!(val.get_signer_name().get_name(), "example.com");
-                assert_eq!(val.get_signature(), "abcdefg");
+                assert_eq!(val.get_signature(), b"abcdefg".to_vec());
             }
             _ => {}
         }