(js) Split string when pasting multiple addresses

Fixes #4097

NEWS

@@ -7,6 +7,7 @@ New features
 Enhancements
  - [web] constrain event/task reminder to a positive number
  - [web] display year in day and week views
+ - [web] split string on comma and semicolon when pasting multiple addresses (#4097)
 
 Bug fixes
  - [core] handle broken CalDAV clients sending bogus SENT-BY (#3992)

UI/WebServerResources/js/Mailer/MessageEditorController.js

@@ -253,11 +253,15 @@
     function addRecipient(contact, field) {
       var recipients, recipient, list;
 
-      if (angular.isString(contact))
-        return contact;
-
       recipients = vm.message.editable[field];
 
+      if (angular.isString(contact)) {
+        _.forEach(contact.split(/[,;]/), function(address) {
+          recipients.push(address);
+        });
+        return null;
+      }
+
       if (contact.$isList({expandable: true})) {
         // If the list's members were already fetch, use them
         if (angular.isDefined(contact.refs) && contact.refs.length) {