Never version of Symfony::Config don't allow multiple root elements like we use for the A/B test campaign definitions. Instead, a configuration must have one root element.
- Campaign definition files have one root element
- The CampaignConfigurationclass doesn't call the deprecated root method any more.
Let's take the opportunity to structure the configuration a bit more, adding the ability to add metadata outside of campaigns if needed (e.g. for ignored buckets like the one in CampaignUtilizationValidator). I suggest a structure like:
bucket_tests: campaigns: campaign_name1: .... campaign_name2: .... ignored_buckets: - 'foo'