PIN verification, notifications, multiple notif providers

Discord, Email & Telegram can be enabled, although email is always
enabled right now (will fix). Also apparently markdown hyperlinks don't
work in Discord, eventually will implement something to convert them to
embeds.

lang/common/en-us.json

@@ -17,6 +17,8 @@
         "linkTelegram": "Link Telegram",
         "contactEmail": "Contact through Email",
         "contactTelegram": "Contact through Telegram",
+        "linkDiscord": "Link Discord",
+        "contactDiscord": "Contact through Discord",
         "theme": "Theme"
     }
 }

lang/form/en-us.json

@@ -18,14 +18,16 @@
         "confirmationRequired": "Email confirmation required",
         "confirmationRequiredMessage": "Please check your email inbox to verify your address.",
         "yourAccountIsValidUntil": "Your account will be valid until {date}.",
-        "sendPIN": "Send the PIN below to the bot, then come back here to link your account."
+        "sendPIN": "Send the PIN below to the bot, then come back here to link your account.",
+        "sendPINDiscord": "Type {command} in {server_channel} on Discord, then send the PIN below via DM to the bot."
     },
     "notifications": {
         "errorUserExists": "User already exists.",
         "errorInvalidCode": "Invalid invite code.",
         "errorTelegramVerification": "Telegram verification required.",
-        "errorInvalidPIN": "Telegram PIN is invalid.",
-        "telegramVerified": "Telegram account verified."
+        "errorDiscordVerification": "Discord verification required.",
+        "errorInvalidPIN": "PIN is invalid.",
+        "verified": "Account verified."
     },
     "validationStrings": {
         "length": {