private static boolean isGrpcAscii(byte[] value) {
        for (byte b : value) {
            if (b < 32 || b > 126) {
                return false;
            }
        }
        return true;
    }
Returns whether the metadata value is a valid gRPC header value, which is only allowed to be readable
ASCII.
grpc/src/main/java/com/linecorp/armeria/internal/common/grpc/MetadataUtil.java