POST /walkers — create, and mapping the response

Create returns 201, not 200

POST /walkers brings a new walker into existence, so the honest status code is 201 Created, not 200. Nest already knows this: a @Post() handler defaults to 201 when it returns normally — you get the right code for free. (Reach for @HttpCode(200) only when you deliberately want to override it.)

The body is validated by the same DTO-plus-ValidationPipe pattern from module 06. Define what a create accepts — note it does not accept id, rating, or createdAt; those are the database's to assign, never the client's: