Add option for minimum account age for contacting modmail

Saw this on the to-do list and decided to give it a shot. Tested and works without issues for me. I advise testing yourself before merging, there's always a chance I missed something since your code is quite extended to work through.

README.md

@@ -84,3 +84,5 @@ These go in `config.json`. See also `config.example.json`.
 |typingProxy|false|If enabled, any time a user is typing to modmail in their DMs, the modmail thread will show the bot as "typing"|
 |typingProxyReverse|false|If enabled, any time a moderator is typing in a modmail thread, the user will see the bot "typing" in their DMs|
 |mentionRole|"here"|Role that is mentioned when new threads are created or the bot is mentioned. Accepted values are "here", "everyone", or a role id as a string. Set to null to disable these pings entirely.|
+|userOlderThan|null|The amount of days the user's account has to exist. If the user's account is not old enough, the bot will not make a new thread and reply to the user with the message defined in `userDeniedMessage`.|
+|userDeniedMessage|"Your Discord account is not old enough to contact modmail."|The message to reply to a user when their account is not old enough to contact modmail.|

src/config.js

@@ -65,6 +65,9 @@ const defaultConfig = {
   "greetingMessage": null,
   "greetingAttachment": null,
 
+  "userOlderThan": null, // Amount of days
+  "userDeniedMessage": "Your Discord account is not old enough to contact modmail.",
+
   "relaySmallAttachmentsAsAttachments": false,
 
   "port": 8890,

src/data/threads.js

@@ -56,6 +56,18 @@ async function createNewThreadForUser(user, quiet = false) {
     throw new Error('Attempted to create a new thread for a user with an existing open thread!');
   }
 
+  // Check the config for a requirement of account age to contact modmail,
+  // if the account is too young, return an optional message without making a new thread
+  if (config.userOlderThan) {
+    if (user.createdAt > moment() - config.userOlderThan * 86400000){
+      if (config.userDeniedMessage) {
+        const privateChannel = await user.getDMChannel();
+        await privateChannel.createMessage(config.userDeniedMessage);
+      }
+      return;
+    } 
+  }
+
   // Use the user's name+discrim for the thread channel's name
   // Channel names are particularly picky about what characters they allow, so we gotta do some clean-up
   let cleanName = transliterate.slugify(user.username);

src/main.js

@@ -86,7 +86,7 @@ bot.on('messageCreate', async msg => {
       thread = await threads.createNewThreadForUser(msg.author);
     }
 
-    await thread.receiveUserReply(msg);
+    if (thread) await thread.receiveUserReply(msg);
   });
 });