Configuring a file-backed HTTP resource for attribute filters

[Rod Widdowson]

I guess it's obvious, but it only just occurred to me that there are two
layers of caching here.  The Apache client is doing some caching and then we
do something which isn't really caching (keep hold of the file in case the
link goes away).  So I *think* that the conditional get thing is all done in
the apache client - in which case that is what we get to debug. Oh joy.

Keith if you put in a case, can you (a) assign it to me (because I just live
to debug HTTP connection issues) and (b) put in a URL that I can test
against (if that’s possible).

Thanks