Rewrite electricity-logger to use an sqlite3 database

include/electricity/server/configuration.hpp

@@ -0,0 +1,33 @@
+#pragma once
+#include <chrono>
+#include <mutex>
+#include <string>
+
+namespace Server
+{
+    class Configuration {
+    private:
+        std::string logDirectory;
+        std::string serverDomain;
+        std::string lastExternalIp;
+        std::chrono::time_point<std::chrono::steady_clock> lastIpCheckTimePoint;
+        std::mutex externalIpRefreshMutex;
+
+        Configuration();
+        Configuration(Configuration & other) = delete;
+        Configuration(Configuration && other) = delete;
+        Configuration & operator=(Configuration & other) = delete;
+        Configuration & operator=(Configuration && other) = delete;
+
+        void RefreshExternalIp();
+        bool ExternalIpRequiresRefresh() const;
+
+    public:
+        void Setup(std::string & electricityLogDirectory, std::string const & serverDomain);
+
+        std::string const & GetLogDirectory() const;
+        std::string const & GetExternalServerIp();
+
+        static Configuration & Get();
+    };
+}