public GrpcClientBuilder callCredentials(CallCredentials callCredentials) {
        requireNonNull(callCredentials, "callCredentials");
        return option(CALL_CREDENTIALS.newValue(callCredentials));
    }
Sets the {@link CallCredentials} that carries credential data that will be propagated to the server
via request metadata.
grpc/src/main/java/com/linecorp/armeria/client/grpc/GrpcClientBuilder.java