[libcalamares] Add a base class for Config-objects

This is an optional (until 3.3) base class, which can handle
Presets consistently for configurations.

src/libcalamares/modulesystem/Config.cpp

@@ -0,0 +1,64 @@
+/* === This file is part of Calamares - <https://calamares.io> ===
+ *
+ *   SPDX-FileCopyrightText: 2021 Adriaan de Groot <groot@kde.org>
+ *   SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ *   Calamares is Free Software: see the License-Identifier above.
+ *
+ */
+
+#include "Config.h"
+
+#include "Preset.h"
+#include "utils/Variant.h"
+
+namespace Calamares
+{
+namespace ModuleSystem
+{
+
+
+class Config::Private
+{
+public:
+    std::unique_ptr< Presets > m_presets;
+};
+
+
+Config::Config( QObject* parent )
+    : QObject( parent )
+    , d( std::make_unique< Private >() )
+{
+}
+
+Config::~Config() {}
+
+void
+Config::loadPresets( const QVariantMap& configurationMap )
+{
+    const QString key( "presets" );
+    if ( !configurationMap.contains( key ) )
+    {
+        d->m_presets.reset();
+        return;
+    }
+    bool bogus = true;
+    d->m_presets = std::make_unique< Presets >( CalamaresUtils::getSubMap( configurationMap, key, bogus ) );
+}
+
+void
+Config::loadPresets( const QVariantMap& configurationMap, const QStringList& recognizedKeys )
+{
+    const QString key( "presets" );
+    if ( !configurationMap.contains( key ) )
+    {
+        d->m_presets.reset();
+        return;
+    }
+    bool bogus = true;
+    d->m_presets
+        = std::make_unique< Presets >( CalamaresUtils::getSubMap( configurationMap, key, bogus ), recognizedKeys );
+}
+
+}  // namespace ModuleSystem
+}  // namespace Calamares