added client management panel

- added classes for displaying the client management panel
- added class for displaying the client info
- added page to display a list of clients
- added page to display OpenVpn client information
- added diagram with OpenVpn certificate revocation process

client/ui/models/clientManagementModel.cpp

@@ -0,0 +1,75 @@
+#include "clientManagementModel.h"
+
+ClientManagementModel::ClientManagementModel(std::shared_ptr<Settings> settings, QObject *parent) :
+    m_settings(settings),
+    QAbstractListModel(parent)
+{
+
+}
+
+void ClientManagementModel::clearData()
+{
+    beginResetModel();
+    m_content.clear();
+    endResetModel();
+}
+
+void ClientManagementModel::setContent(const QVector<ClientInfo> &data)
+{
+    beginResetModel();
+    m_content = data;
+    endResetModel();
+}
+
+int ClientManagementModel::rowCount(const QModelIndex &parent) const
+{
+    Q_UNUSED(parent);
+    return static_cast<int>(m_content.size());
+}
+
+QVariant ClientManagementModel::data(const QModelIndex &index, int role) const
+{
+    if (!index.isValid() || index.row() < 0
+            || index.row() >= static_cast<int>(m_content.size())) {
+        return QVariant();
+    }
+
+    if (role == NameRole) {
+        return m_content[index.row()].name;
+    }
+    if (role == CertIdRole) {
+        return m_content[index.row()].certId;
+    }
+    if (role == CertDataRole) {
+        return m_content[index.row()].certData;
+    }
+    return QVariant();
+}
+
+void ClientManagementModel::setData(const QModelIndex &index, QVariant data, int role)
+{
+    if (!index.isValid() || index.row() < 0
+            || index.row() >= static_cast<int>(m_content.size())) {
+        return;
+    }
+
+    if (role == NameRole) {
+         m_content[index.row()].name = data.toString();
+    }
+    if (role == CertIdRole) {
+        m_content[index.row()].certId = data.toString();
+    }
+    if (role == CertDataRole) {
+        m_content[index.row()].certData = data.toString();
+    }
+    emit dataChanged(index, index);
+}
+
+QHash<int, QByteArray> ClientManagementModel::roleNames() const
+{
+    QHash<int, QByteArray> roles;
+    roles[NameRole] = "clientName";
+    roles[CertIdRole] = "certId";
+    roles[CertDataRole] = "certData";
+    return roles;
+}