Add support for SecretValue being requested as a stream

The print node uses a stream interface to print all incoming objects. Since `core/secret@v1`  now returns an actual secret, not just a string, secrets started being printed as their struct representation `{my-key}`

Author: sebastianrath

core/inputs.go

@@ -952,6 +952,8 @@ func convertToReader(c *ExecutionState, value reflect.Value) (io.Reader, error)
 		return strings.NewReader(v), nil
 	case []byte:
 		return bytes.NewReader(v), nil
+	case SecretValue:
+		return strings.NewReader(v.Secret), nil
 	default:
 		return nil, CreateErr(c, nil, "unsupported type '%s'", GetTypeNameSafe(value.Type()))
 	}