Initial backend test for user-based data/customizations (#4144)

Right now only support for colors and no real UX, idea is to test it & allow the idea to grow while figuring out the UX

src/controllers/userdata/UserData.hpp

@@ -0,0 +1,71 @@
+#pragma once
+
+#include "util/RapidJsonSerializeQString.hpp"
+#include "util/RapidjsonHelpers.hpp"
+
+#include <QColor>
+#include <QString>
+#include <boost/optional.hpp>
+#include <pajlada/serialize.hpp>
+
+namespace chatterino {
+
+// UserData defines a set of data that is defined for a unique user
+// It can contain things like optional replacement color for the user, a unique alias
+// or a user note that should be displayed with the user
+// Replacement fields should be optional, where none denotes that the field should not be updated for the user
+struct UserData {
+    boost::optional<QColor> color{boost::none};
+
+    // TODO: User note?
+};
+
+}  // namespace chatterino
+
+namespace pajlada {
+
+template <>
+struct Serialize<chatterino::UserData> {
+    static rapidjson::Value get(const chatterino::UserData &value,
+                                rapidjson::Document::AllocatorType &a)
+    {
+        rapidjson::Value obj;
+        obj.SetObject();
+        if (value.color)
+        {
+            const auto &color = *value.color;
+            chatterino::rj::set(obj, "color",
+                                color.name().toUtf8().toStdString(), a);
+        }
+        return obj;
+    }
+};
+
+template <>
+struct Deserialize<chatterino::UserData> {
+    static chatterino::UserData get(const rapidjson::Value &value,
+                                    bool *error = nullptr)
+    {
+        if (!value.IsObject())
+        {
+            PAJLADA_REPORT_ERROR(error)
+            return chatterino::UserData{};
+        }
+
+        chatterino::UserData user;
+
+        QString colorString;
+        if (chatterino::rj::getSafe(value, "color", colorString))
+        {
+            QColor color(colorString);
+            if (color.isValid())
+            {
+                user.color = color;
+            }
+        }
+
+        return user;
+    }
+};
+
+}  // namespace pajlada