Updating a customer without a birthday sets the birthday to the current dat

[niklasnatter]

When the birthday property is omitted (or not set) on a PUT request to the /me endpoint, the birthday of the current customer is set to the current date.

The UpdateCustomerRequest class declares the birthday class-property as nullable, therefore I assume that it should be possible to omit the birthday property from this request (eg. if the customer does not want to specify his birthday).
https://github.com/Sylius/ShopApiPlugin/blob/master/src/Request/Customer/UpdateCustomerRequest.php#L25

This behaviour happens because the UpdateCustomerHandler constructs a new DateTimeImmutable object with the birthday property of the UpdateCustomerRequest. If this property is null, the constructed DateTimeImmutable object will contain the current date.
https://github.com/Sylius/ShopApiPlugin/blob/master/src/Handler/Customer/UpdateCustomerHandler.php#L31

[mamazu]

This looks like a bug. Besides the fact that the request class doesn't return a datetime immutable anyways. This looks like a missing typecheck on the command.