[AI Bundle][Platform] Make the structured output validation groups configurable

[marco-jouwweb]

Q	A
Bug fix?	no
New feature?	yes
Docs?	yes
Issues	-
License	MIT

ValidatorSubscriber always validates the populated structured output object in the Default validation group. When the target class is an existing domain object that already carries Default constraints for other purposes (forms, API input), the only ways out are decorating the subscriber or moving every existing constraint to custom groups. As discussed with @chr-hertel on Slack, this PR makes the groups configurable instead.

Platform

ValidatorSubscriber gets an optional groups argument accepting the same values as ValidatorInterface::validate() (a group name, a list of groups, or a GroupSequence). It is passed through ValidatorResultConverter to the buffered validation call and to PartialObjectStreamListener::setValidator(), so the final object of a streamed structured output is validated in the same groups.

$dispatcher->addSubscriber(new PlatformSubscriber());
$dispatcher->addSubscriber(new ValidatorSubscriber(groups: ['ai']));

A single call can override them with the validation_groups option. Like PlatformSubscriber does for response_format, the subscriber consumes the option on InvocationEvent so it is never merged into the provider request, and applies it on ResultEvent:

$platform->invoke('gpt-4o', $messages, [
    'response_format' => Invoice::class,
    'validation_groups' => ['ai', 'strict'],
]);

AI Bundle

New structured_output.validation_groups option, applied to the ai.platform.structured_output.validator_subscriber service as the default groups. It is a top-level node (not under platform, whose children are the bridge types). An empty list keeps the current behavior; configuring groups while symfony/validator is missing throws the same kind of "requires package" exception as the other optional integrations.

ai:
    structured_output:
        validation_groups: ['ai']

final class Invoice
{
    #[Assert\NotBlank(groups: ['ai'])]
    public string $customer = '';

    #[Assert\Positive] // "Default" group only, skipped for model output
    public int $total = 0;
}

Notes

• All new parameters are optional and last, so there is no BC break; null keeps validating in the validator's default group.
• Out of scope on purpose: ValidatorConstraintsDescriber still describes constraints of every group in the generated JSON schema.

🤖 Generated with Claude Code

[marco-jouwweb]

Not very happy with this union type.. WDYT?