Implement sending stickers

MSC2545 image packs are used as source.

src/imagepackevent.cpp

@@ -0,0 +1,54 @@
+// SPDX-FileCopyrightText: 2021-2023 Tobias Fella <tobias.fella@kde.org>
+// SPDX-License-Identifier: LGPL-2.0-or-later
+
+#include "imagepackevent.h"
+#include <QJsonObject>
+
+using namespace Quotient;
+
+ImagePackEventContent::ImagePackEventContent(const QJsonObject &json)
+{
+    if(json.contains(QStringLiteral("pack"))) {
+        pack = ImagePackEventContent::Pack{
+            fromJson<Omittable<QString>>(json["pack"].toObject()["display_name"]),
+#ifdef QUOTIENT_07
+            fromJson<Omittable<QUrl>>(json["pack"].toObject()["avatar_url"]),
+#else
+            QUrl(),
+#endif
+            fromJson<Omittable<QStringList>>(json["pack"].toObject()["usage"]),
+            fromJson<Omittable<QString>>(json["pack"].toObject()["attribution"]),
+        };
+    } else {
+        pack = none;
+    }
+
+    const auto &keys = json["images"].toObject().keys();
+    for (const auto &k : keys) {
+        Omittable<EventContent::ImageInfo> info;
+        if (json["images"][k].toObject().contains(QStringLiteral("info"))) {
+#ifdef QUOTIENT_07
+            info = EventContent::ImageInfo(QUrl(json["images"][k]["url"].toString()), json["images"][k]["info"].toObject(), k);
+#else
+            info = EventContent::ImageInfo(QUrl(json["images"][k]["url"].toString()), json["images"][k].toObject(), k);
+#endif
+        } else {
+            info = none;
+        }
+        images += ImagePackImage{
+            k,
+#ifdef QUOTIENT_07
+            fromJson<QUrl>(json["images"][k]["url"].toString()),
+#else
+            QUrl(),
+#endif
+            fromJson<Omittable<QString>>(json["images"][k]["body"]),
+            info,
+            fromJson<Omittable<QStringList>>(json["images"][k]["usage"]),
+        };
+    }
+}
+
+void ImagePackEventContent::fillJson(QJsonObject* o) const {
+    // TODO
+}