Dispatch /dims3/ on the handler

[beetlebugorg]

What

dims_handler dispatches /dims3/ on the handler name. The container image sets each legacy handler from the environment: DIMS_ENABLE_DIMS3 defaults to off, DIMS_ENABLE_DIMS4 defaults to on.

Why

The dispatch matched the URI as well as the handler name:

(r->uri && strncmp(r->uri, "/dims3/", 7) == 0)

That test ran before any handler check, so the module responded to a /dims3/ request on any server that loaded it. I removed the <Location /dims3/> block from the running image and requested the path: the module responded with 500 from its own allowlist check. SetHandler None gave the same result. An operator had no way to stop serving /dims3/ short of unloading the module.

/dims4/, /dims5/, and dims-status dispatch on the handler name. /dims3/ now does the same.

Verify

make -C test test
make -C test sanitize
make -C test test-update

281 cases pass, 105 sanitizer cases report no finding, and every golden file reproduces. TestDims3HandlerRemoved and TestDims4HandlerRemoved request both paths on a server that sets SetHandler None, and expect 404. TestLegacyEndpointsServedWhereConfigured requests them on the default server and expects a status other than 404.

Against the built image:

docker run -d -p 8000:8000 mod-dims:ci
curl -o /dev/null -w '%{http_code}\n' \
  'http://127.0.0.1:8000/dims3/development/resize/100x100/?url=http://example.com/a.png'

I measured 404 with the image defaults and 500 with -e DIMS_ENABLE_DIMS3=on. The same run with -e DIMS_ENABLE_DIMS4=off returned 404 for /dims4/.

Breaking

A server that loads the module and has no <Location /dims3/> block stops serving /dims3/. A server whose configuration sets the handler is unaffected.

The image stops serving /dims3/ unless DIMS_ENABLE_DIMS3 is on. A deployment that uses /dims3/ through the image sets it.