Add database upgrade files.

These files contain the sequence of SQL commands needed to bring
a database or project schema up to date with the latest template
database or project schema.

These files must be applied manually. Check the comments at the top of
the file for instructions.

etc/db/upgrades/upgrade01-78adb2be→7917eeeb.sql

@@ -0,0 +1,22 @@
+-- Upgrade the database from commit 78adb2be to 7917eeeb.
+--
+-- This upgrade affects the `public` schema only.
+--
+-- It creates a new table, `info`, for storing arbitrary JSON
+-- data not belonging to a specific project. Currently used
+-- for the equipment list, it could also serve to store user
+-- details, configuration settings, system state, etc.
+--
+-- To apply, run as the dougal user:
+--
+-- psql < $THIS_FILE
+--
+-- NOTE: It will fail harmlessly if applied twice.
+
+
+CREATE TABLE IF NOT EXISTS public.info (
+    key text NOT NULL primary key,
+    value jsonb
+);
+
+CREATE TRIGGER info_tg AFTER INSERT OR DELETE OR UPDATE ON public.info FOR EACH ROW EXECUTE FUNCTION public.notify('info');