Brand guidelines are now default for new PMax campaigns in the UI; API follows in v21.
Business name and logo assets now live at the campaign level
(CampaignAsset), not in AssetGroupAsset.
API users must update code to support both asset locations.
Existing campaigns are being automatically migrated (if assets are consistent);
Full rollout by Oct 30, 2025.
Use Campaign.brand_guidelines_enabled to manage or detect this setting.
