archive: push restic backup and prune metrics, and add a backups dashboard

nix/script-tests/otlp-gauges.nix

@@ -0,0 +1,27 @@
+# `checks.script-test-otlp-gauges` — runs ../host-modules/lib/otlp-gauges.nix's
+# `otlp_gauges` against a stub `curl`, with an endpoint and without. The cases
+# are in ./otlp-gauges.sh.
+{
+  pkgs,
+  ...
+}:
+let
+  render =
+    endpoint:
+    pkgs.writeText "otlp-gauges.sh" (
+      import ../host-modules/lib/otlp-gauges.nix { inherit (pkgs) lib; } { inherit endpoint; }
+    );
+in
+pkgs.runCommand "hyperhive-script-test-otlp-gauges"
+  {
+    nativeBuildInputs = [
+      pkgs.coreutils
+      pkgs.jq
+    ];
+    FUNCTIONS = render "http://10.42.0.1:4318";
+    FUNCTIONS_NO_ENDPOINT = render null;
+  }
+  ''
+    ${pkgs.bash}/bin/bash ${./otlp-gauges.sh}
+    touch "$out"
+  ''