feat: added sender rewriting scheme (closes forwardemail#148, closes forwardemail#169, closes forwardemail#137)

Author: niftylettuce

.env.defaults

@@ -27,3 +27,5 @@ RATELIMIT_MAX=300
 VANITY_DOMAINS=secret.fyi,hash.fyi,mailsire.com,hideaddress.net
 LOOKUP_ENDPOINT=https://forwardemail.net:4000/v1/lookup
 LOOKUP_SECRETS=secret,
+SRS_SECRET=
+SRS_DOMAIN=forwardemail.net

.env.schema

@@ -27,3 +27,5 @@ RATELIMIT_MAX=
 VANITY_DOMAINS=
 LOOKUP_ENDPOINT=
 LOOKUP_SECRETS=
+SRS_SECRET=
+SRS_DOMAIN=

config.js

@@ -1,13 +1,11 @@
 const CustomError = require('./custom-error');
 const MessageSplitter = require('./message-splitter');
-const createMessageID = require('./create-message-id');
 const env = require('./env');
 const logger = require('./logger');
 
 module.exports = {
   CustomError,
   MessageSplitter,
-  createMessageID,
   env,
   logger
 };