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;
};