add vendoring

vendor/maunium.net/go/mautrix/util/dbutil/samples/01-sample.sql

@@ -0,0 +1,21 @@
+-- v0 -> v3: Sample revision jump
+CREATE TABLE foo (
+	-- only: postgres
+	key BIGINT PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY,
+	-- only: sqlite
+	key INTEGER PRIMARY KEY,
+
+	data JSONB NOT NULL
+);
+
+-- only: sqlite until "end only"
+CREATE TRIGGER test AFTER INSERT ON foo WHEN NEW.data->>'action' = 'delete' BEGIN
+	DELETE FROM test WHERE key <= NEW.data->>'index';
+END;
+-- end only sqlite
+-- only: postgres until "end only"
+CREATE FUNCTION delete_data() RETURNS TRIGGER LANGUAGE plpgsql AS $$ BEGIN
+	DELETE FROM test WHERE key <= NEW.data->>'index';
+	RETURN NEW;
+END $$;
+-- end only postgres