Add last active admin functionality

The implementation is mostly based on DU4L#16
but we update the timer in the database instead of the frontend.
The update is done when the user fetches the profile,
so for every first load done in a new tab in the browser.

Please note that this commit can NOT be merged before TFNS#213
is merged since the migration files are now not consecutive.
The other PR contains a migration with ID 41, so this PR has a migration
with ID 42 (and this answers everything of course).
The migration will fail in this branch therefore. For testing, please
rename the file and use a throw away database.

api/migrations/42-add-last-active.sql

@@ -0,0 +1,33 @@
+ALTER TABLE ctfnote.profile
+ADD COLUMN "lastactive" timestamptz NOT NULL DEFAULT CURRENT_TIMESTAMP;
+
+
+/* UpdateLastActive */
+CREATE FUNCTION ctfnote.update_last_active ()
+  RETURNS void
+  AS $$
+  BEGIN
+    UPDATE ctfnote.profile
+      SET lastactive = now()
+      WHERE id = ctfnote_private.user_id ();
+  END;
+$$
+LANGUAGE plpgsql VOLATILE
+SECURITY DEFINER;
+GRANT EXECUTE ON FUNCTION ctfnote.update_last_active () TO user_guest;
+
+CREATE OR REPLACE FUNCTION ctfnote.me ()
+  RETURNS ctfnote.profile
+  AS $$
+  SELECT ctfnote.update_last_active();
+  SELECT
+    *
+  FROM
+    ctfnote.profile
+  WHERE
+    id = ctfnote_private.user_id ()
+  LIMIT 1;
+
+$$
+LANGUAGE SQL
+STRICT STABLE;