[AB-333] providing some dates as separate instants instead of relying on the member attributes

truncating date to day when displaying the date for export emote stats
fixing wrong message when confirming a command and adding missing exception handling

abstracto-application/abstracto-modules/modmail/modmail-impl/src/main/java/dev/sheldan/abstracto/modmail/service/ModMailThreadServiceBean.java

@@ -425,6 +425,7 @@ public class ModMailThreadServiceBean implements ModMailThreadService {
                 .builder()
                 .member(member)
                 .latestModMailThread(latestThread)
+                .memberJoinDate(member.getTimeJoined().toInstant())
                 .pastModMailThreadCount((long)oldThreads.size())
                 .build();
         List<CompletableFuture<Message>> messages = channelService.sendEmbedTemplateInTextChannelList("modmail_thread_header", header, channel);

abstracto-application/abstracto-modules/modmail/modmail-int/src/main/java/dev/sheldan/abstracto/modmail/model/template/ModMailThreaderHeader.java

@@ -6,6 +6,8 @@ import lombok.Getter;
 import lombok.Setter;
 import net.dv8tion.jda.api.entities.Member;
 
+import java.time.Instant;
+
 /**
  * This is the model used when a new mod mail thread is opened and a message containing some information about the user
  * is displayed for the user handling the mod mail thread.
@@ -23,6 +25,7 @@ public class ModMailThreaderHeader {
      * for the user
      */
     private ModMailThread latestModMailThread;
+    private Instant memberJoinDate;
     /**
      * The amount of previous mod mail thread the user has.
      */