ref(omemo): add qomemo/variant

qomemo/variant/omemo_base.h

@@ -0,0 +1,31 @@
+/*
+ * Created by victoria on 2021-05-13.
+ */
+
+#pragma once
+
+class QXmppElement;
+class QXmppIq;
+
+namespace QXmpp::Omemo {
+
+class Device;
+class DeviceList;
+
+namespace Variant {
+
+class Base {
+public:
+  virtual ~Base() = default;
+
+  virtual QXmppElement deviceToXml(const Device& device) = 0;
+  virtual Device deviceFromXml(const QXmppElement& xml) = 0;
+
+  virtual QXmppElement deviceListToXml(const DeviceList& deviceList) = 0;
+  virtual DeviceList deviceListFromXml(const QXmppElement& xml) = 0;
+  virtual QXmppIq deviceListSetIq(const DeviceList& deviceList) = 0;
+};
+
+} // namespace Variant
+
+} // namespace QXmpp::Omemo