Add a feature flag for Simplified Sliding Sync. (#3057)

* Disable SSS when logging out.

* Bump the SDK.

NSE/Sources/NotificationServiceExtension.swift

@@ -86,7 +86,10 @@ class NotificationServiceExtension: UNNotificationServiceExtension {
                 // It's imperative that we create **at most** one UserSession/Client per process
                 Task.synchronous { [appHooks] in
                     do {
-                        Self.userSession = try await NSEUserSession(credentials: credentials, clientSessionDelegate: keychainController, appHooks: appHooks)
+                        Self.userSession = try await NSEUserSession(credentials: credentials,
+                                                                    clientSessionDelegate: keychainController,
+                                                                    simplifiedSlidingSyncEnabled: settings.simplifiedSlidingSyncEnabled,
+                                                                    appHooks: appHooks)
                     } catch {
                         MXLog.error("Failed creating user session with error: \(error)")
                     }

NSE/Sources/Other/NSESettingsProtocol.swift

@@ -18,6 +18,7 @@ import Foundation
 
 protocol NSESettingsProtocol {
     var logLevel: TracingConfiguration.LogLevel { get }
+    var simplifiedSlidingSyncEnabled: Bool { get }
 }
 
 extension AppSettings: NSESettingsProtocol { }

NSE/Sources/Other/NSEUserSession.swift

@@ -25,7 +25,7 @@ final class NSEUserSession {
                                                                                imageCache: .onlyOnDisk)
     private let delegateHandle: TaskHandle?
 
-    init(credentials: KeychainCredentials, clientSessionDelegate: ClientSessionDelegate, appHooks: AppHooks) async throws {
+    init(credentials: KeychainCredentials, clientSessionDelegate: ClientSessionDelegate, simplifiedSlidingSyncEnabled: Bool, appHooks: AppHooks) async throws {
         userID = credentials.userID
         if credentials.restorationToken.passphrase != nil {
             MXLog.info("Restoring client with encrypted store.")
@@ -36,6 +36,7 @@ final class NSEUserSession {
             .baseBuilder(setupEncryption: false,
                          httpProxy: URL(string: homeserverURL)?.globalProxy,
                          sessionDelegate: clientSessionDelegate,
+                         simplifiedSlidingSyncEnabled: simplifiedSlidingSyncEnabled,
                          appHooks: appHooks)
             .sessionPath(path: credentials.restorationToken.sessionDirectory.path(percentEncoded: false))
             .username(username: credentials.userID)