feat: migration file for versioning

supabase/migrations/20240610132742_lesson_language_versioning.sql

@@ -0,0 +1,25 @@
+CREATE TABLE lesson_language_history (
+  id SERIAL PRIMARY KEY,
+  lesson_language_id INTEGER REFERENCES lesson_language(id),
+  old_content TEXT,
+  new_content TEXT,
+  timestamp TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
+);
+
+CREATE FUNCTION update_lesson_language_history()
+  RETURNS trigger AS $$
+BEGIN
+  IF TG_OP IN ('INSERT', 'UPDATE') THEN
+    INSERT INTO lesson_language_history (lesson_language_id, old_content, new_content)
+    VALUES (NEW.id, COALESCE(OLD.content, ''), NEW.content);
+  END IF;
+  RETURN NULL;
+END;
+$$ LANGUAGE plpgsql;
+
+
+CREATE TRIGGER update_lesson_language_history_trigger
+AFTER INSERT
+OR
+UPDATE ON lesson_language for each row
+EXECUTE PROCEDURE update_lesson_language_history();