- Refactoring of the mail sending part. Mail queue (table 'queued') is now used also for all test emails.

- More options how to send test emails.
- Fixed problems with pausing a campaign (#593)
- Started rework of transactional sender of templates (#606), however this contains functionality regression at the moment because it does not interpret templates as HBS. It needs HBS option for templates as described in https://github.com/Mailtrain-org/mailtrain/issues/611#issuecomment-502345227

TODO:
- detect sending errors connected to not able to contact the mailer and pause/retry campaing and queued sending - don't mark the recipients as BOUNCED
- add FAILED campaign state and fall into it if sending to campaign consistently fails (i.e. the error with sending is not temporary)
- if the same happends for queued email, delete the message

server/lib/helpers.js

@@ -28,11 +28,11 @@ function filterObject(obj, allowedKeys) {
     return result;
 }
 
-function castToInteger(id) {
+function castToInteger(id, msg) {
     const val = parseInt(id);
 
     if (!Number.isInteger(val)) {
-        throw new Error('Invalid id');
+        throw new Error(msg || 'Invalid id');
     }
 
     return val;