How can I create admin route without adding custom or existing plugin?

If anyone else is looking for solution,
at moment in Strapi V5 to add custom admin route without adding extra plugin, you can do it like this.

In following folder

src/extensions/user-permissions

create

strapi-server.ts

And inside you can add custom admin route like:

export default (plugin: any) => {
  plugin.routes["admin"].routes.push(
    {
      method: "GET",
      path: "/locations",
      handler: async (ctx: { body: any; query: any }) => {
        ctx.body = await strapi.documents("api::rental.location").findMany(ctx.query);
      },
    },
  ... //more routes
  );

  return plugin;
};