refactor(eventsub): conditionally use Howard's date lib (#6048)

Co-authored-by: Nerixyz <nerixdev@outlook.de>

lib/twitch-eventsub-ws/src/chrono.cpp

@@ -1,16 +1,22 @@
 #include "twitch-eventsub-ws/chrono.hpp"
 
-#include "twitch-eventsub-ws/date.h"
+#include "twitch-eventsub-ws/detail/errors.hpp"
 
-#include <sstream>
+#if __cpp_lib_chrono >= 201907L
+#    include <chrono>
+using namespace std::chrono;
+#else
+#    include <date/date.h>
+using namespace date;
+#endif
 
 namespace chatterino::eventsub::lib {
 
 boost::json::result_for<std::chrono::system_clock::time_point,
                         boost::json::value>::type
-    tag_invoke(
-        boost::json::try_value_to_tag<std::chrono::system_clock::time_point>,
-        const boost::json::value &jvRoot, const AsISO8601 &)
+    tag_invoke(boost::json::try_value_to_tag<
+                   std::chrono::system_clock::time_point> /*tag*/,
+               const boost::json::value &jvRoot, const AsISO8601 & /*tag*/)
 {
     const auto raw = boost::json::try_value_to<std::string>(jvRoot);
     if (raw.has_error())
@@ -18,10 +24,18 @@ boost::json::result_for<std::chrono::system_clock::time_point,
         return raw.error();
     }
 
-    std::chrono::system_clock::time_point tp;
+    std::chrono::time_point<std::chrono::system_clock, std::chrono::nanoseconds>
+        tp;
     std::istringstream in{*raw};
-    in >> date::parse("%FT%H:%M:%12SZ", tp);
+    in >> parse("%FT%H:%M:%12SZ", tp);
 
-    return tp;
+    if (!in.good())
+    {
+        EVENTSUB_BAIL_HERE(error::Kind::BadTimeFormat);
+    }
+
+    return std::chrono::time_point_cast<std::chrono::system_clock::duration>(
+        tp);
 }
+
 }  // namespace chatterino::eventsub::lib