fix(serializer): apply API Platform name converter to input/output DTOs

[soyuka]

Q	A
Branch?	main
Tickets	Fixes #7705
License	MIT
Doc PR	∅

When denormalizing input DTOs, the serializer re-enters without the input context key, causing supportsDenormalization() to reject the DTO. It falls through to Symfony's ObjectNormalizer which lacks AP's name converter. A new api_platform_input context flag ensures the DTO is handled by AbstractItemNormalizer.

[mbeccati]

The patch seems to be fixing my original use case, thanks

[ceesvanegmond]

@soyuka This PR actually breaks certain Input DTO's like this (with no defaults to null options)

<?php

readonly class UpdateAccount
{
    public function __construct(
        public readonly string $email,
        public readonly ?string $firstName,
    ) {}
}

Cannot create an instance of \u0022Domain\\Account\\Model\\Dto\\CreateAccount\u0022 from serialized data because its constructor requires the following parameters to be present $firstName

Reverting back to 4.2.16 it works. According to the symfony docs it by default $firstName should be null in this case:
https://symfony.com/doc/current/serializer.html#require-all-properties

Changing it to this, it works. But it's not 100% BC

<?php

readonly class UpdateAccount
{
    public function __construct(
        public readonly string $email,
        public readonly ?string $firstName = null,
    ) {}
}