Copy over Morgan's work

Author: morganchen12

FirebaseAuth/Sources/Swift/ActionCode/ActionCodeInfo.swift

@@ -15,7 +15,7 @@
 import Foundation
 
 /// Manages information regarding action codes.
-@objc(FIRActionCodeInfo) open class ActionCodeInfo: NSObject {
+@objc(FIRActionCodeInfo) public final class ActionCodeInfo: NSObject, Sendable {
   /// The operation being performed.
   @objc public let operation: ActionCodeOperation
 

FirebaseAuth/Sources/Swift/ActionCode/ActionCodeSettings.swift

@@ -15,7 +15,8 @@
 import Foundation
 
 /// Used to set and retrieve settings related to handling action codes.
-@objc(FIRActionCodeSettings) open class ActionCodeSettings: NSObject {
+@objc(FIRActionCodeSettings) open class ActionCodeSettings: NSObject,
+  @unchecked Sendable /* TODO: sendable */ {
   /// This URL represents the state/Continue URL in the form of a universal link.
   ///
   /// This URL can should be constructed as a universal link that would either directly open