Gui: Add YamlParameterSource for StyleParameters

This adds ability to read and write Style Parameters from YAML files.
This will allow to move certain tokens out of the User Parameter system
to ensure that they can be update without user needing to reapply the
theme.

src/Gui/StyleParameters/ParameterManager.cpp

@@ -26,6 +26,10 @@
 #include "ParameterManager.h"
 #include "Parser.h"
 
+#include <QFile>
+#include <fstream>
+#include <yaml-cpp/yaml.h>
+
 #ifndef _PreComp_
 #include <QColor>
 #include <QRegularExpression>
@@ -35,6 +39,8 @@
 #include <variant>
 #endif
 
+FC_LOG_LEVEL_INIT("Gui", true, true)
+
 namespace Gui::StyleParameters
 {
 
@@ -215,6 +221,81 @@ void UserParameterSource::remove(const std::string& name)
     hGrp->RemoveASCII(name.c_str());
 }
 
+YamlParameterSource::YamlParameterSource(const std::string& filePath, const Metadata& metadata)
+    : ParameterSource(metadata)
+    , filePath(filePath)
+{
+    QFile file(QString::fromStdString(filePath));
+
+    if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) {
+        FC_TRACE("StyleParameters: Unable to open file " << filePath);
+        return;
+    }
+
+    if (filePath.starts_with(":/")) {
+        this->metadata.options |= ReadOnly;
+    }
+
+    QTextStream in(&file);
+    std::string content = in.readAll().toStdString();
+
+    YAML::Node root = YAML::Load(content);
+    for (auto it = root.begin(); it != root.end(); ++it) {
+        auto key = it->first.as<std::string>();
+        auto value = it->second.as<std::string>();
+
+        parameters[key] = Parameter {
+            .name = key,
+            .value = value,
+        };
+    }
+}
+
+std::list<Parameter> YamlParameterSource::all() const
+{
+    std::list<Parameter> result;
+    for (const auto& param : parameters | std::views::values) {
+        result.push_back(param);
+    }
+    return result;
+}
+
+std::optional<Parameter> YamlParameterSource::get(const std::string& name) const
+{
+    if (auto it = parameters.find(name); it != parameters.end()) {
+        return it->second;
+    }
+
+    return std::nullopt;
+}
+
+void YamlParameterSource::define(const Parameter& param)
+{
+    parameters[param.name] = param;
+}
+
+void YamlParameterSource::remove(const std::string& name)
+{
+    parameters.erase(name);
+}
+
+void YamlParameterSource::flush()
+{
+    YAML::Node root;
+    for (const auto& [name, param] : parameters) {
+        root[name] = param.value;
+    }
+
+    QFile file(QString::fromStdString(filePath));
+    if (!file.open(QIODevice::WriteOnly | QIODevice::Truncate | QIODevice::Text)) {
+        FC_TRACE("StyleParameters: Unable to open file " << filePath);
+        return;
+    }
+
+    QTextStream out(&file);
+    out << QString::fromStdString(YAML::Dump(root));
+}
+
 ParameterManager::ParameterManager() = default;
 
 void ParameterManager::reload()