post
https://sandbox-api.viantinc.com/{basePath}/creative
Create a new creative via POST. Supports multiple creative kinds: Custom Tag (BANNER+TAG), Hosted Banner, Video (VAST URL/XML/Hosted), Audio, Native, and DOOH. Provide creativeType, creativeSubtype, type.mediaType, and type-specific payload; omit id. One of advertiserId or campaignId is required.