Support for unique fields (e.g. slug, uuid) when translating entities

[CreativeNative]

Problem

When translating entities that contain unique fields (e.g. uuid, slug), the current translation process copies these values 1:1 to the new translation.
This leads to unique constraint violations on the database level:

• uuid → copied, violates UNIQUE
• slug → copied, violates UNIQUE

Attributes like #[EmptyOnTranslate] or #[SharedAmongstTranslations] do not solve this problem for unique fields.

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Example

#[ORM\Column(type: "string", length: 255, unique: true)]
private string $slug;

When creating a translation, the slug value is copied → UNIQUE constraint failed.

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Possible Solutions

1. Schema-based fix (quick solution):
   Use a composite unique index on slug + locale instead of a global unique on slug.
   See Quick Fix for unique fields in the README.

   #[ORM\UniqueConstraint(
       name: "uniq_slug_locale",
       columns: ["slug", "locale"]
   )]

2. Bundle improvement (long-term):
   Add a handler for unique fields in the translator:

   • Respect #[EmptyOnTranslate] → set field to NULL
   • Regenerate new values for uuid or slug (e.g. via SluggerInterface, Uuid::v4())
   • Throw a clear exception if no strategy is possible

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Why it matters

Without handling unique fields, entities with slugs or UUIDs cannot be translated safely.
Supporting this would make the bundle more robust for real-world use cases.