README for SwiftUI alpha release

Author: russellwheatley

FirebaseSwiftUI/README.md

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+# FirebaseUI for SwiftUI (Alpha release)
+
+## Installation
+
+1. Launch Xcode and open the project or workspace where you want to add the packages.
+2. In the menu bar, go to: `File > Add Package Dependencies...`
+3. Enter the Package URL: `https://github.com/firebase/FirebaseUI-iOS`
+4. Select target(s) you wish to add to your app (currently `FirebaseAuthSwiftUI`, `FirebaseGoogleSwiftUI`, `FirebaseFacebookSwiftUI` and `FirebasePhoneAuthSwiftUI` are available). `FirebaseAuthSwiftUI` is required and contains Email provider API.
+5. Press `Add Packages` button to complete installation.
+
+
+## Getting started
+
+1. Follow step 2, 3 & 5 on [adding Firebase to your SwiftUI app](https://firebase.google.com/docs/ios/setup).
+2. You should now update your app entry point to look like this:
+
+```swift
+import FirebaseAuthSwiftUI
+import FirebaseCore
+import SwiftUI
+
+class AppDelegate: NSObject, UIApplicationDelegate {
+  func application(_ application: UIApplication,
+                   didFinishLaunchingWithOptions launchOptions: [
+                     UIApplication.LaunchOptionsKey: Any
+                   ]?) -> Bool {
+    FirebaseApp.configure()
+    return true
+  }
+}
+
+@main
+struct FirebaseSwiftUIExampleApp: App {
+  @UIApplicationDelegateAdaptor(AppDelegate.self) var appDelegate
+
+  init() {}
+
+  var body: some Scene {
+    WindowGroup {
+        ContentView()
+    }
+  }
+}
+
+struct ContentView: View {
+  let authService: AuthService
+
+  init() {
+    let configuration = AuthConfiguration()
+
+    authService = AuthService(
+      configuration: configuration,
+    )
+    .withEmailSignIn()
+  }
+
+  var body: some View {
+    AuthPickerView().environment(authService)
+  }
+}
+```
+
+3. For a more complete example, see the [SwiftUI sample app](https://github.com/firebase/FirebaseUI-iOS/tree/main/samples/swiftui/FirebaseSwiftUIExample).
+
+## Configuration options
+
+You can create an `AuthConfiguration` instance and pass it to the `AuthService` as demonstrated above. Here are the options:
+
+```swift
+public struct AuthConfiguration {
+  // hides cancel buttons when you don't want a flow to be interrupted
+  let shouldHideCancelButton: Bool
+  // stop users from being able to swipe away sheets/modal
+  let interactiveDismissEnabled: Bool
+  // automatically upgrade anonymous users so that they are linked with account being used to sign-in
+  let shouldAutoUpgradeAnonymousUsers: Bool
+  // custom string bundle for string localizations
+  let customStringsBundle: Bundle?
+  // terms of service URL
+  let tosUrl: URL
+  // privacy policy URL
+  let privacyPolicyUrl: URL
+  // action code settings for email sign in link
+  let emailLinkSignInActionCodeSettings: ActionCodeSettings?
+  // action code settings verifying email address
+  let verifyEmailActionCodeSettings: ActionCodeSettings?
+
+  public init(shouldHideCancelButton: Bool = false,
+              interactiveDismissEnabled: Bool = true,
+              shouldAutoUpgradeAnonymousUsers: Bool = false,
+              customStringsBundle: Bundle? = nil,
+              tosUrl: URL = URL(string: "https://example.com/tos")!,
+              privacyPolicyUrl: URL = URL(string: "https://example.com/privacy")!,
+              emailLinkSignInActionCodeSettings: ActionCodeSettings? = nil,
+              verifyEmailActionCodeSettings: ActionCodeSettings? = nil)
+}
+```
+
+## Configuring providers
+
+1. Ensure the provider is installed from step 1 (e.g. if configuring Google provider, you need to install `FirebaseGoogleSwiftUI` package).
+2. Ensure you have called the relevant API on `AuthService` to initialise provider. Example of Email and Google provider initialization:
+
+```swift
+let authService = AuthService()
+    .withEmailSignIn()
+    .withGoogleSignIn()
+```
+
+> Note: There may be additional setup for each provider typically in the AppDelegate. [See example app for setup.](https://github.com/firebase/FirebaseUI-iOS/tree/main/samples/swiftui/FirebaseSwiftUIExample) 
+
+
+## API available for alpha release
+1. General API
+   - Auto upgrade anonymous user account linking (if configured).
+   - Sign out
+2. Email/Password
+   - Sign-in/Create user
+   - Password recovery
+   - Email link sign-in
+3. Google
+   - Sign in with Google
+4. Facebook
+   1. Sign in with Facebook limited login
+   2. Sign in with Facebook classic login 
+5. Phone Auth
+   - Verify phone number
+   - Sign in with phone number 
+6. User
+   - Update password
+   - Delete user
+   - Verify email address
+
+## Notes for Alpha release
+1. Customization/theming for Views is not yet available.
+2. The providers available are Email, Phone, Google and Facebook.
+3. String localizations have been ported over and used where possible from the previous implementation, but new strings will only have English translations for the time being.
+4. The UI has not been polished and is subject to change once design has been finalized.