Set TikTok brand identity

Set or update the Brand Identity (display name + avatar) for a tiktokads SocialAccount. TikTok requires every ad to carry an identity_id + identity_type pair. The Brand Identity is the CUSTOMIZED_USER alternative to attributing ads to a real @username (TT_USER). This route uploads the supplied image to TikTok, creates the identity via /v2/identity/create/, and caches the resulting identity_id on the account so subsequent POST /v1/ads/create calls can opt into it via identityType: 'CUSTOMIZED_USER'.

Configurable on every tiktokads account, including linked-mode ones (those with a posting account on the same profile). Configuration is idempotent and harmless when posting is also connected: the default ad-create path still prefers TT_USER, and CUSTOMIZED_USER is only used per-ad when the caller explicitly opts in.

TikTok identities are immutable post-creation. Re-saving creates a new identity on TikTok and swaps the cached id; the old identity stays orphaned on TikTok's side (harmless, no billing impact).

Alternative: pass brandIdentity directly on POST /v1/ads/create to configure on first ad creation in a single round-trip.