contacts API changes

In iOS 18, there are several changes to the Contacts API aimed at improving privacy and user control. Here are the key updates:

New Authorization Flow: iOS 18 introduces a two-stage prompt for apps requesting access to contacts. The first stage asks if contacts should be shared, and the second stage offers the option of providing limited or full access. This flow is automatically presented when your app requests access to contacts, enhancing transparency and control for users.
Contact Access Button: A new feature called the Contact Access Button allows apps to add contacts incrementally without requiring full access. This button fits within your app's UI and can grant access to new contacts with a single tap, providing a more seamless user experience.
Authorization Levels: There are now four authorization levels for accessing contacts. With full access, an app can read and modify any contact. Limited access allows reading and modifying only the contacts granted access. Apps start with a "not determined" status and must present an authorization prompt to access the contact store.
Incremental Contact Sharing: For apps that offer features like searching for mail recipients, iOS 18 allows adding contacts incrementally using the contact access button, which provides results for contacts that the app doesn't have full access to.

For more detailed information, you can refer to the sessions What’s new in privacy and Meet the Contact Access Button.