added some utility methods to bot service

reworked message cache to not be jda messages, but own objects: cachedMessages, jda messages should not be kept around
added listener to listen for message links, to represent them in an embed (or embeds)
added offsetDateTime handling for gson
introduced a way on how to handle async transaction handling for suggestions and message loading (self reference with another method with transactional)
added timestamp support to embeds

abstracto-application/abstracto-modules/moderation/moderation-impl/src/main/resources/templates/listener/message_deleted/message_deleted_embed_en_US.ftl

@@ -12,11 +12,11 @@
   "fields": [
     {
       "name": ":x: Original Message: ",
-      "value": "${message.contentRaw}"
+      "value": "${message.content}"
     },
     {
         "name": "Link",
-        "value": "[${textChannel.name}](${message.jumpUrl})"
+        "value": "[${textChannel.name}](${message.messageUrl})"
     }
   ]
 }

abstracto-application/abstracto-modules/moderation/moderation-impl/src/main/resources/templates/listener/message_deleted/message_deleted_en_US.ftl

@@ -1,2 +1,2 @@
 Message from ${member.effectiveName} (${member.idLong?c}) deleted in ${textChannel.asMention}.
-Message: ${message.contentRaw}
+Message: ${message.content}