Create a custom conversion goal

Create a new conversion destination on the platform. Supported for LinkedIn (conversion rule) and Google Ads (conversion action). Meta and OpenAI Ads pixels are created via their own tracking-tags flow instead (`POST /v1/accounts/{accountId}/tracking-tags`); this endpoint returns 405 for both. **LinkedIn:** creation is NOT idempotent. A retry creates a second destination. Deduplicate before retrying. **Google Ads:** calling with a name that already exists reuses the existing conversion action transparently (the response is identical to a fresh create). Calling with the same name but a different category returns a typed `IDEMPOTENCY_CONFLICT` (409) rather than silently returning the mismatched action. **LinkedIn:** the rule is created with `conversionMethod=CONVERSIONS_API` and (by default) auto-associated with all of the ad account's campaigns via `autoAssociationType=ALL_CAMPAIGNS`. Pass `autoAssociationType: NONE` to opt out and manage associations explicitly via the associations endpoints below. 365-day attribution windows are only valid for `SUBMIT_APPLICATION`, `PURCHASE`, `ADD_TO_CART`, `QUALIFIED_LEAD`, and `LEAD` rule types; the API rejects other combinations locally. **Google Ads:** the conversion action is created with `type=UPLOAD_CLICKS` (required for API-uploaded offline conversions, immutable after creation). The `type` field carries the Google `ConversionActionCategory` enum value, e.g. `PURCHASE`, `SUBSCRIBE_PAID`, `SIGNUP`, `IMPORTED_LEAD`, `BOOK_APPOINTMENT`. Unified standard event names (e.g. `Purchase`, `Subscribe`, `CompleteRegistration`, `Lead`, `Schedule`) are resolved to their Google category equivalents automatically. The action defaults to secondary (non-primary) to avoid immediately steering Smart Bidding; pass `primaryForGoal: true` to opt in.