Update ad account settings

Sets the default DSA beneficiary and payor on a Meta ad account (EU DSA, Article 26). Set them once and every EU-targeted call to /v1/ads/create, /v1/ads/boost and /v1/ads/ctwa on that ad account can omit dsaBeneficiary/dsaPayor: Meta applies the defaults automatically.

The values are written to the ad account on Meta, the same setting Ads Manager edits. Nothing is stored in Zernio, and defaults already set in Ads Manager work identically. Zernio never guesses these values for you. Beneficiary and payor are legal disclosures shown to EU users, so you must provide the entity names explicitly. Use GET /v1/ads/dsa-recommendations to offer suggestions in your UI.

If defaultDsaPayor is omitted, the beneficiary is also set as the payor, which covers the common case where the same entity benefits from and pays for the ads. Read the current values back with GET /v1/ads/dsa-defaults.

Currently supported for Meta accounts only; other platforms return 400.