Until the iOS SDK ships, integrate with plain HTTPS.

Create an install ID
On first launch, generate a UUID and keep it in the Keychain, so it survives reinstalls on the same device. Never regenerate it.
Call /v1/init on every launch
Send a signed POST https://attribution.ondropp.app/v1/init with platform: "ios" and your iOS SDK key. iOS has no install referrer, so leave installReferrer out. See the request and response.
Handle Universal Links
Set up Universal Links so links open your app directly when it's installed.

Use the iOS SDK key in your iOS app. A request whose platform doesn't match its key's platform is rejected with platform_mismatch.

iOS integration