Add button to view pinned messages in a room

BUG: 497427

src/models/pinnedmessagemodel.h

@@ -0,0 +1,62 @@
+// SPDX-FileCopyrightText: 2025 Joshua Goins <josh@redstrate.com>
+// SPDX-License-Identifier: LGPL-2.0-or-later
+
+#pragma once
+
+#include <QAbstractListModel>
+#include <QQmlEngine>
+#include <QString>
+
+#include <Quotient/csapi/rooms.h>
+
+#include "messagemodel.h"
+#include "neochatroommember.h"
+
+namespace Quotient
+{
+class Connection;
+}
+
+class NeoChatRoom;
+
+/**
+ * @class PinnedMessageModel
+ *
+ * This class defines the model for visualising a room's pinned messages.
+ */
+class PinnedMessageModel : public MessageModel
+{
+    Q_OBJECT
+    QML_ELEMENT
+
+    /**
+     * @brief Whether the model is currently loading.
+     */
+    Q_PROPERTY(bool loading READ loading NOTIFY loadingChanged)
+
+public:
+    explicit PinnedMessageModel(QObject *parent = nullptr);
+
+    /**
+     * @brief Number of rows in the model.
+     *
+     * @sa QAbstractItemModel::rowCount
+     */
+    int rowCount(const QModelIndex &parent = QModelIndex()) const override;
+
+    bool loading() const;
+
+Q_SIGNALS:
+    void loadingChanged();
+
+protected:
+    std::optional<std::reference_wrapper<const Quotient::RoomEvent>> getEventForIndex(QModelIndex index) const override;
+
+private:
+    void setLoading(bool loading);
+    void fill();
+
+    bool m_loading = false;
+
+    std::vector<Quotient::event_ptr_tt<Quotient::RoomEvent>> m_pinnedEvents;
+};