Move the qt models to their own folder

Felt like the src folder was getting a bit crowded so move all the models to a folder named models.

src/models/collapsestateproxymodel.h

@@ -0,0 +1,21 @@
+// SPDX-FileCopyrightText: 2022 Tobias Fella <fella@posteo.de>
+// SPDX-License-Identifier: LGPL-2.0-or-later
+
+#pragma once
+
+#include "messageeventmodel.h"
+#include <QSortFilterProxyModel>
+
+class CollapseStateProxyModel : public QSortFilterProxyModel
+{
+    Q_OBJECT
+public:
+    enum Roles {
+        AggregateDisplayRole = MessageEventModel::LastRole + 1,
+    };
+    [[nodiscard]] bool filterAcceptsRow(int source_row, const QModelIndex &source_parent) const override;
+    [[nodiscard]] QHash<int, QByteArray> roleNames() const override;
+    [[nodiscard]] QVariant data(const QModelIndex &idx, int role = Qt::DisplayRole) const override;
+
+    [[nodiscard]] QString aggregateEventToString(int row) const;
+};