@Deprecated
    @Override
    public AbstractWebClientBuilder rpcDecorator(DecoratingRpcClientFunction decorator) {
        throw new UnsupportedOperationException("RPC decorator cannot be added to the web client builder.");
    }
Raises an {@link UnsupportedOperationException} because this builder doesn't support RPC-level but only
HTTP-level decorators.

@deprecated RPC decorator cannot be added to the web client builder.
core/src/main/java/com/linecorp/armeria/client/AbstractWebClientBuilder.java