refactor(client): extract config handling into a new class

include/config.hpp

@@ -0,0 +1,31 @@
+#pragma once
+
+#include <json/json.h>
+
+#include <string>
+
+namespace waybar {
+
+class Config {
+ public:
+  Config() = default;
+
+  void load(const std::string &config, const std::string &style);
+
+  const std::string &getStyle() { return css_file_; }
+
+  Json::Value &getConfig() { return config_; }
+
+  std::vector<Json::Value> getOutputConfigs(const std::string &name, const std::string &identifier);
+
+ private:
+  void setupConfig(const std::string &config_file, int depth);
+  void resolveConfigIncludes(Json::Value &config, int depth);
+  void mergeConfig(Json::Value &a_config_, Json::Value &b_config_);
+
+  std::string config_file_;
+  std::string css_file_;
+
+  Json::Value config_;
+};
+}  // namespace waybar