TF-2384 Handle NSE to get plain notification in iOS

Signed-off-by: dab246 <tdvu@linagora.com>
(cherry picked from commit 364f32a14b9888f73a3a103b8b5e1bc9b31e148e)

ios/TwakeMailNSE/Keychain/KeyChainControllerDelegate.swift

@@ -0,0 +1,12 @@
+import Foundation
+
+struct KeychainCredentials {
+    let accountId: String
+    let sharingSession: KeychainSharingSession
+}
+
+protocol KeychainControllerDelegate: AnyObject {
+    func retrieveSharingSessionFromKeychain(accountId: String) -> KeychainSharingSession?
+    func retrieveSharingSessions() -> [KeychainCredentials]
+    func updateEmailStateToKeychain(accountId: String, newState: String)
+}