default ByteBufAllocator alloc() {
        throw new UnsupportedOperationException("No ByteBufAllocator available for this RequestContext.");
    }
Returns the {@link ByteBufAllocator} for this {@link RequestContext}. Any buffers created by this
{@link ByteBufAllocator} must be
<a href="https://netty.io/wiki/reference-counted-objects.html">reference-counted</a>. If you don't know
what this means, you should probably use {@code byte[]} or {@link ByteBuffer} directly instead
of calling this method.
core/src/main/java/com/linecorp/armeria/common/RequestContext.java