feat: Allow regerating a device's id

lib/src/omemo/device.dart

@@ -163,6 +163,23 @@ class Device {
     );
   }
 
+  /// Returns a new device that is equal to this one with the exception that the new
+  /// device's id is a new number between 0 and 2**32 - 1.
+  @internal
+  Device withNewId() {
+    return Device(
+      jid,
+      generateRandom32BitNumber(),
+      ik,
+      spk,
+      spkId,
+      spkSignature,
+      oldSpk,
+      oldSpkId,
+      opks,
+    );
+  }
+  
   /// Converts this device into an OmemoBundle that could be used for publishing.
   Future<OmemoBundle> toBundle() async {
     final encodedOpks = <int, String>{};

lib/src/omemo/sessionmanager.dart

@@ -458,6 +458,28 @@ class OmemoSessionManager {
     });
   }
 
+  /// Generates an entirely new device. May be useful when the user wants to reset their cryptographic
+  /// identity. Triggers an event to commit it to storage.
+  Future<void> regenerateDevice({ int opkAmount = 100 }) async {
+    await _deviceLock.synchronized(() async {
+      _device = await Device.generateNewDevice(_device.jid, opkAmount: opkAmount);
+
+      // Commit it
+      _eventStreamController.add(DeviceModifiedEvent(_device));
+    });
+  }
+
+  /// Make our device have a new identifier. Only useful before publishing it as a bundle
+  /// to make sure that our device has a id that is account unique.
+  Future<void> regenerateDeviceId() async {
+    await _deviceLock.synchronized(() async {
+      _device = _device.withNewId();
+
+      // Commit it
+      _eventStreamController.add(DeviceModifiedEvent(_device));
+    });
+  }
+  
   @visibleForTesting
   OmemoDoubleRatchet getRatchet(String jid, int deviceId) => _ratchetMap[RatchetMapKey(jid, deviceId)]!;