feat: add column created_by to role_user table (#5594)

As it says in the title. Adds a created_by column to the role_user table
to more easily track who's doing what.

src/migrations/20231211133008-add-created-by-to-role-user.js

@@ -0,0 +1,7 @@
+exports.up = function(db, cb) {
+  db.runSql(`ALTER TABLE role_user ADD COLUMN created_by INTEGER`, cb);
+};
+
+exports.down = function(db, cb) {
+  db.runSql(`ALTER TABLE role_user DROP COLUMN created_by`, cb);
+};