feat: schedule job that removes expired keys

packages/at_client/lib/src/manager/storage_manager.dart

@@ -41,6 +41,7 @@ class StorageManager {
         .getSecondaryKeyStoreManager()!;
     await hiveKeyStore.initialize();
     keyStoreManager.keyStore = hiveKeyStore;
+    manager.scheduleKeyExpireTask(preferences!.expiryCheckTimeIntervalMins);
     isStorageInitialized = true;
   }
 }

packages/at_client/lib/src/preference/at_client_preference.dart

@@ -66,6 +66,9 @@ class AtClientPreference {
 
   Duration monitorHeartbeatInterval = Duration(seconds: 10);
 
+  /// Time interval for the scheduled task that removes expired keys from local keyStore
+  int expiryCheckTimeIntervalMins = 10;
+
   ///[OptionalParameter] when set to true logs TLS Keys to file.
   bool decryptPackets = false;