Add descriptions for endpoints for use in openapi

src/Vegasco.Server.Api/Cars/CreateCar.cs

@@ -17,6 +17,7 @@ public static class CreateCar
 		return builder
 			.MapPost("cars", Endpoint)
 			.WithTags("Cars")
+			.WithDescription("Creates a new car")
 			.Produces<Response>(201)
 			.ProducesValidationProblem();
 	}