fix(users/Profpatsch/openlab-tools): add cache headers

This is a dumb experiment to see how hard it is to respect cache
headers; turns out, medium hard but doable.

Sets the correct expiry time according to the cache, plus respects
`If-Modified-Since` which is a tiny bit harder.

Change-Id: I9e6166af0fa254df2beb0f3919187b91a407487b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9810
Autosubmit: Profpatsch <mail@profpatsch.de>
Tested-by: BuildkiteCI
Reviewed-by: Profpatsch <mail@profpatsch.de>

users/Profpatsch/hie.yaml

@@ -24,6 +24,12 @@ cradle:
       component: "jbovlaste-sqlite:exe:jbovlaste-sqlite"
     - path: "./whatcd-resolver/src"
       component: "lib:whatcd-resolver"
+    - path: "./whatcd-resolver/Main.hs"
+      component: "whatcd-resolver:exe:whatcd-resolver"
+    - path: "./openlab-tools/src"
+      component: "lib:openlab-tools"
+    - path: "./openlab-tools/Main.hs"
+      component: "openlab-tools:exe:openlab-tools"
     - path: "./ircmail/src"
       component: "lib:ircmail"
     - path: "./httzip/Httzip.hs"