Request and handle PniIdentity sync message

ts/textsecure/messageReceiverEvents.ts

@@ -349,6 +349,20 @@ export class KeysEvent extends ConfirmableEvent {
   }
 }
 
+export type PNIIdentityEventData = Readonly<{
+  publicKey: Uint8Array;
+  privateKey: Uint8Array;
+}>;
+
+export class PNIIdentityEvent extends ConfirmableEvent {
+  constructor(
+    public readonly data: PNIIdentityEventData,
+    confirm: ConfirmCallback
+  ) {
+    super('pniIdentity', confirm);
+  }
+}
+
 export type StickerPackEventData = Readonly<{
   id?: string;
   key?: string;