gluon-status-page: add generic respondd cgi-bin

Adding a cgi-bin script which allows to query a node's respondd over HTTP.
This is especially useful when the response is expected to be large and
a UDP response would lead to an unreliable transfer of multiple IP
fragments, like for the upcoming "statistics-extended" respondd
provider. HTTP/TCP is then the more reliable approach.

Query examples with HTTP GET:

  $ curl --compressed "http://<IP6ADDR>/cgi-bin/respondd"
  -> defaults to nodeinfo

  $ curl --compressed "http://<IP6ADDR>/cgi-bin/respondd?nodeinfo+statistics"

Query examples with HTTP POST:

  $ curl --data "" --compressed "http://<IP6ADDR>/cgi-bin/respondd"
  -> defaults to nodeinfo

  $ curl --data "nodeinfo statistics" --compressed "http://<IP6ADDR>/cgi-bin/respondd"

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>

package/gluon-status-page/files/lib/gluon/status-page/www/cgi-bin/respondd

@@ -0,0 +1,35 @@
+#!/bin/sh
+
+badrequest() {
+	echo 'Status: 400 Bad Request'
+	echo
+	exit 1
+}
+
+case "${REQUEST_METHOD}" in
+  GET)
+	;;
+  POST)
+	QUERY_STRING="$(cat)"
+	;;
+  *)
+	badrequest
+	;;
+esac
+
+if [ -z "${QUERY_STRING}" ]; then
+	# default to nodeinfo
+	QUERY_STRING="nodeinfo"
+else
+	# replace URL encoded spaces via '+' with real space
+	QUERY_STRING="${QUERY_STRING//+/ }"
+fi
+
+
+# Return deflate compressed ("GET" prefix), JSON formatted response
+
+echo "Content-Type: application/json"
+echo "Content-Encoding: deflate"
+echo ""
+
+exec gluon-neighbour-info -i lo -d ::1 -p 1001 -r "GET ${QUERY_STRING}"