[PATCH] add documentation about backend naming for VMOD authors

[Dridi Boukelmoune]

> The way we solve that problem in kernels is to name the VCL_HasBackend()
> function VCL_CreateBackend() and allowing it to fail :-)

Why not keep VRT_new_backend as the only interface for VMODs and allow
this one to fail? (or do the atomic auto-renaming if needed)

> So far I have kept the CLI away from VMODs, but that is probably
> not viable in the long term.
>
> The backend/director split is, as you point out, not clean, and
> if nothing else the naming is horrible.
>
> So I think 5.0 is going to look quite differently than 4.1 in
> this area.

So maybe my narrow thinking is not that narrow if we narrow down the
scope of Geoff's proposal to 4.1 :)

It occurred to me today that I was replying with 4.1 in mind and that
it may not be the case for you.

Best,
Dridi