Fix conversion warnings on 32 bits

src/utils/time.cpp

@@ -9,9 +9,10 @@
 
 namespace utils
 {
-std::string to_string(const std::time_t& timestamp)
+std::string to_string(const std::chrono::system_clock::time_point::rep& time)
 {
   constexpr std::size_t stamp_size = 21;
+  const std::time_t timestamp = static_cast<std::time_t>(time);
   char date_buf[stamp_size];
   if (std::strftime(date_buf, stamp_size, "%FT%TZ", std::gmtime(&timestamp)) != stamp_size - 1)
     return "";

src/utils/time.hpp

@@ -2,9 +2,10 @@
 
 #include <ctime>
 #include <string>
+#include <chrono>
 
 namespace utils
 {
-std::string to_string(const std::time_t& timestamp);
+std::string to_string(const std::chrono::system_clock::time_point::rep& timestamp);
 std::time_t parse_datetime(const std::string& stamp);
-}
+}