Adapt a create_media_buy request for a v2 server.
Strips v3-only top-level fields, converts brand → brand_manifest, derives
buyer_ref (top-level + per-package) from idempotency_key, and adapts
packages.
v2.5 requires buyer_ref as the buyer's reference for THIS media buy,
top-level + per-package. v3 doesn't model buyer_ref but idempotency_key
carries the same client-controlled-unique-identity semantics. Reusing it
preserves the idempotency contract sellers depend on for deduping replays:
the same v3 request always produces the same v2.5 buyer_ref. Caller-
supplied buyer_ref (if any) always wins.
Adapt a create_media_buy request for a v2 server. Strips v3-only top-level fields, converts brand → brand_manifest, derives
buyer_ref(top-level + per-package) fromidempotency_key, and adapts packages.v2.5 requires
buyer_refas the buyer's reference for THIS media buy, top-level + per-package. v3 doesn't modelbuyer_refbutidempotency_keycarries the same client-controlled-unique-identity semantics. Reusing it preserves the idempotency contract sellers depend on for deduping replays: the same v3 request always produces the same v2.5buyer_ref. Caller- suppliedbuyer_ref(if any) always wins.