Campaign email sending manager in golang.
- ✅ Create campaign with emails
- ✅ List campaigns created by the user
- ✅ Show details of a campaign created by the user
- ✅ Delete campaign
- ✅ Update campaign
- ✅ Send campaign emails
- ✅ Worker to send emails marked as pending
- ✅ User authentication
- ✅ Mapped application with tests