Make status mandatory.

migrations/20210307184428_make_status_not_null_in_subscriptions.sql

@@ -0,0 +1,11 @@
+-- We wrap the whole migration in a transaction to make sure
+-- it succeeds or fails atomically.
+-- `sqlx` does not do it automatically for us.
+BEGIN;
+    -- Backfill `status` for historical entries
+    UPDATE subscriptions
+        SET status = 'confirmed'
+        WHERE status IS NULL;
+    -- Make `status` mandatory
+    ALTER TABLE subscriptions ALTER COLUMN status SET NOT NULL;
+COMMIT;