…listed in the input (Christian Kolb)This PR was merged into the 6.3 branch.Discussion----------[Serializer] Add flag to require all properties to be listed in the input| Q             | A| ------------- | ---| Branch?       | 6.3| Bug fix?      | no| New feature?  | yes| Deprecations? | no| Tickets       |Fix#49504| License       | MIT| Doc PR        |symfony/symfony-docs#17979The PR#40522 introduced a fallback for nullable properties to be set to `null` when they aren't provided as parameters.A drawback of that approach is that it easier for bugs to appear through typos or renamings of those properties. I think the current implementation makes perfect sense as a default. Therefore, this PR introduces a new context flag that prevents that fallback behaviour. This way nothing changes for existing systems, but for people wanting more control, it's possible to set a flag.### Example```phpfinal class Product{    public function __construct(        public string $name,        public ?int $costsInCent,    ) {    }}// This works and results in $costsInCent as null$product = $this->serializer->deserialize(    '{"name": "foo"}',    Product::class,    JsonEncoder::FORMAT,);// When using the flag, only the following JSON is valid$product = $this->serializer->deserialize(    '{"name": "foo", "costsInCent": null}',    Product::class,    JsonEncoder::FORMAT,    [        AbstractNormalizer::PREVENT_NULLABLE_FALLBACK => true,    ],);// This would result in an error due to missing parameters$product = $this->serializer->deserialize(    '{"name": "foo"}',    Product::class,    JsonEncoder::FORMAT,    [        AbstractNormalizer::PREVENT_NULLABLE_FALLBACK => true,    ],);```Commits-------d62410a [Serializer] Add flag to require all properties to be listed in the input