refactor: phone auth provider

Author: russellwheatley

FirebaseSwiftUI/FirebasePhoneAuthSwiftUI/Sources/Services/PhoneAuthProviderAuthUI.swift

@@ -77,3 +77,16 @@ public class PhoneAuthProviderAuthUI: AuthProviderUI {
     AnyView(PhoneAuthButtonView(phoneProvider: provider as! PhoneAuthProviderSwift))
   }
 }
+
+public class PhoneAuthProviderAuthUI: AuthProviderUI {
+  public var provider: AuthProviderSwift
+  public let id: String = "phone.com"
+
+  public init(provider: PhoneAuthProviderSwift? = nil) {
+    self.provider = provider ?? PhoneProviderSwift()
+  }
+
+  @MainActor public func authButton() -> AnyView {
+    AnyView(PhoneAuthButtonView(phoneProvider: provider as! PhoneAuthProviderSwift))
+  }
+}