Add menu to invite users

include/dialogs/InviteUsers.h

@@ -0,0 +1,41 @@
+#pragma once
+
+#include <QFrame>
+#include <QLabel>
+#include <QListWidgetItem>
+#include <QStringList>
+
+class FlatButton;
+class TextField;
+class QListWidget;
+
+namespace dialogs {
+
+class InviteUsers : public QFrame
+{
+        Q_OBJECT
+public:
+        explicit InviteUsers(QWidget *parent = nullptr);
+
+protected:
+        void paintEvent(QPaintEvent *event) override;
+
+signals:
+        void closing(bool isLeaving, QStringList invitees);
+
+private slots:
+        void removeInvitee(QListWidgetItem *item);
+
+private:
+        void addUser();
+        QStringList invitedUsers() const;
+
+        FlatButton *confirmBtn_;
+        FlatButton *cancelBtn_;
+
+        TextField *inviteeInput_;
+        QLabel *errorLabel_;
+
+        QListWidget *inviteeList_;
+};
+} // dialogs