added sqlite db backend progress

include/matador/sql/connection.hpp

@@ -1,32 +1,36 @@
 #ifndef QUERY_CONNECTION_HPP
 #define QUERY_CONNECTION_HPP
 
-#include "matador/sql/query_intermediates.hpp"
+#include "matador/sql/connection_info.hpp"
 #include "matador/sql/dialect.hpp"
-#include "matador/sql/query_builder.hpp"
+#include "matador/sql/query_result.hpp"
+#include "matador/sql/record.hpp"
 
 #include <string>
 
 namespace matador::sql {
 
+class connection_impl;
+
 class connection
 {
 public:
-  connection() = default;
-  explicit connection(std::string dns);
+  explicit connection(connection_info info);
+  explicit connection(const std::string& dns);
+  ~connection();
 
   void open();
   void close();
   [[nodiscard]] bool is_open() const;
-
-  [[nodiscard]] const std::string& dns() const;
+  [[nodiscard]] const connection_info& info() const;
 
   query_result<record> fetch(const std::string &sql);
   std::pair<size_t, std::string> execute(const std::string &sql);
 
 private:
-  std::string dns_;
+  const connection_info connection_info_;
   bool is_open_{false};
+  connection_impl *connection_{};
 };
 
 }