retrieve slug from slugs table if the $slugAttribute field was not changed

[zeezo887]

Description

The changes made here was to use the previous slug value if the $slugAttribute field was not changed. By doing this, we won't have duplicate slug entries when a model is not updated via the repository.

/**
 * Returns changed value of slugAttribute field or previous slug value
 */
private function getSlugValue($slugAttribute, $locale): mixed
{
    return $this->wasChanged($slugAttribute)
        ? $this->$slugAttribute
        : $this->slugs()->where('locale', $locale)
            ->where('active', true)->value('slug');
}

Related Issues

Fixes #2681