…-time serialization metadata (nicolas-grekas)This PR was merged into the 7.4 branch.Discussion----------[Serializer] Allow using attributes to declare compile-time serialization metadata| Q             | A| ------------- | ---| Branch?       | 7.4| Bug fix?      | no| New feature?  | yes| Deprecations? | yes| Issues        | -| License       | MITVery close to#61528Prerequisite for#61287At the moment, serialization attributes are read at runtime when `framework.serialization.enable_attributes` is true.This means they don't fit for bundles nor can't they be warmed up.This PR fixes both issues by using a new `serializer.attribute_metadata` resource tag, that's turned into a list of classes to parse for attributes at compile-time.For bundles and for apps, the tag is added by explicit service configuration:```php        ->set('my_bundle.api_resource.product', Product::class)            ->resourceTag('serializer.attribute_metadata')```Unlike validation where we have constraint attributes to auto-discover service resources, serialization doesn't have any corresponding hooks. We do have a few like `#[DiscriminatorMap]` of `#[Groups]`, but relying on those would miss many more classes that are meant for serialization. Maybe we could introduce an attribute that'd hint that some class is serializable by the component (and require the attribute at some point in the future?)Commits-------bc6e054 [Serializer] Allow using attributes to declare compile-time serialization metadata

…ew constraints for a class (nicolas-grekas)This PR was merged into the 7.4 branch.Discussion----------[Validator] Add `#[ExtendsValidationFor]` to declare new constraints for a class| Q             | A| ------------- | ---| Branch?       | 7.4| Bug fix?      | no| New feature?  | yes| Deprecations? | no| Issues        | -| License       | MITThis PR builds on#61528I propose to add a `#[ExtendsValidationFor]` attribute that allows adding validation constraints to another class.This is typically needed for third party classes. For context, Sylius has a nice doc about this:https://docs.sylius.com/the-customization-guide/customizing-validationAt the moment, the only way to achieve this is by declaring the new constraints in the (hardcoded) `config/validation/` folder, using either xml or yaml. No attributes.With this PR, one will be able to define those extra constraints using PHP attributes, set on classes that'd mirror the properties/getters of the targeted class. The compiler pass will ensure that all properties/getters declared in these source classes also exist in the target class. (source = the app's class that declares the new constraints; target = the existing class to add constraints to.)```php#[ExtendsValidationFor(TargetClass::class)]abstract class SourceClass{    #[Assert\NotBlank(groups: ['my_app'])]    #[Assert\Length(min: 3, groups: ['my_app'])]    public string $name = '';    #[Assert\Email(groups: ['my_app'])]    public string $email = '';    #[Assert\Range(min: 18, groups: ['my_app'])]    public int $age = 0;}```(I made the class abstract because it's not supposed to be instantiated - but it's not mandatory.)Here are the basics of how this works:1. During container compilation, classes marked with `#[ExtendsValidationFor(Target::class)]` are collected and validated: the container checks that members declared on the source exist on the target. If not, a `MappingException` is thrown.2. The validator is configured to map the target to its source classes.3. At runtime, when loading validation metadata for the target, attributes (constraints, callbacks, group providers) are read from both the target and its mapped source classes and applied accordingly.Commits-------e884a76 [Validator] Add `#[ExtendsValidationFor]` to declare new constraints for a class