Revert "Use a different Date data type"

This reverts commit 857c7d3972.

src/xmpp/biboumi_component.cpp

@@ -805,7 +805,7 @@ void BiboumiComponent::send_archived_message(const Database::MucLogLine& log_lin
 
     XmlSubNode delay(forwarded, "delay");
     delay["xmlns"] = DELAY_NS;
-    delay["stamp"] = log_line.col<Database::Date>().to_string();
+    delay["stamp"] = utils::to_string(log_line.col<Database::Date>());
 
     XmlSubNode submessage(forwarded, "message");
     submessage["xmlns"] = CLIENT_NS;

src/xmpp/xmpp_component.cpp

@@ -399,7 +399,7 @@ void XmppComponent::send_muc_message(const std::string& muc_name, const std::str
 }
 
 #ifdef USE_DATABASE
-void XmppComponent::send_history_message(const std::string& muc_name, const std::string& nick, const std::string& body_txt, const std::string& jid_to, const DateTime& timestamp)
+void XmppComponent::send_history_message(const std::string& muc_name, const std::string& nick, const std::string& body_txt, const std::string& jid_to, Database::time_point::rep timestamp)
 {
   Stanza message("message");
   message["to"] = jid_to;
@@ -417,7 +417,7 @@ void XmppComponent::send_history_message(const std::string& muc_name, const std:
     XmlSubNode delay(message, "delay");
     delay["xmlns"] = DELAY_NS;
     delay["from"] = muc_name + "@" + this->served_hostname;
-    delay["stamp"] = timestamp.to_string();
+    delay["stamp"] = utils::to_string(timestamp);
   }
 
   this->send_stanza(message);

src/xmpp/xmpp_component.hpp

@@ -6,7 +6,6 @@
 #include <network/tcp_client_socket_handler.hpp>
 #include <database/database.hpp>
 #include <xmpp/xmpp_parser.hpp>
-#include <utils/datetime.hpp>
 #include <xmpp/body.hpp>
 
 #include <unordered_map>
@@ -142,7 +141,7 @@ public:
    * Send a message, with a <delay/> element, part of a MUC history
    */
   void send_history_message(const std::string& muc_name, const std::string& nick, const std::string& body,
-                            const std::string& jid_to, const DateTime& timestamp);
+                            const std::string& jid_to, Database::time_point::rep timestamp);
 #endif
   /**
    * Send an unavailable presence for this nick