feat: add very early mod.toml packwiz support

Also use it as a on-disk format for storing mod metadata. This will be
used later on to make better mod managment.

launcher/modplatform/packwiz/Packwiz.cpp

@@ -0,0 +1,60 @@
+#include "Packwiz.h"
+
+#include "modplatform/ModIndex.h"
+
+#include <QDebug>
+#include <QDir>
+#include <QObject>
+
+auto Packwiz::createModFormat(QDir& index_dir, ModPlatform::IndexedPack& mod_pack, ModPlatform::IndexedVersion& mod_version) -> Mod
+{
+    Mod mod;
+
+    mod.name = mod_pack.name;
+    mod.filename = mod_version.fileName;
+
+    mod.url = mod_version.downloadUrl;
+    mod.hash_format = ModPlatform::ProviderCapabilities::hashType(mod_pack.provider);
+    mod.hash = "";  // FIXME
+
+    mod.provider = mod_pack.provider;
+    mod.file_id = mod_pack.addonId;
+    mod.project_id = mod_version.fileId;
+
+    return mod;
+}
+
+void Packwiz::updateModIndex(QDir& index_dir, Mod& mod)
+{
+    // Ensure the corresponding mod's info exists, and create it if not
+    auto index_file_name = QString("%1.toml").arg(mod.name);
+    QFile index_file(index_dir.absoluteFilePath(index_file_name));
+
+    // There's already data on there!
+    if (index_file.exists()) { index_file.remove(); }
+
+    if (!index_file.open(QIODevice::ReadWrite)) {
+        qCritical() << "Could not open file " << index_file_name << "!";
+        return;
+    }
+
+    // Put TOML data into the file
+    QTextStream in_stream(&index_file);
+    auto addToStream = [&in_stream](QString&& key, QString value) { in_stream << QString("%1 = \"%2\"\n").arg(key, value); };
+
+    {
+        addToStream("name", mod.name);
+        addToStream("filename", mod.filename);
+        addToStream("side", mod.side);
+
+        in_stream << QString("\n[download]\n");
+        addToStream("url", mod.url.toString());
+        addToStream("hash-format", mod.hash_format);
+        addToStream("hash", mod.hash);
+
+        in_stream << QString("\n[update]\n");
+        in_stream << QString("[update.%1]\n").arg(ModPlatform::ProviderCapabilities::providerName(mod.provider));
+        addToStream("file-id", mod.file_id.toString());
+        addToStream("project-id", mod.project_id.toString());
+    }
+}