Do not schedule or delete messages for unpublished events

Ghost User
2018-07-09T09:39:41+02:00

Closes #655 and #656

#### Previous behaviour
Steps to reproduce:

1. Create event (unpublished)
2. See that the message is scheduled

--

1. Create event
2. Let it send
3. Change event
4. Notice that the message is still t...

Closes #655 (closed) and #656 (closed)

Previous behaviour

Steps to reproduce:

1. Create event (unpublished)

2. See that the message is scheduled

--

1. Create event

2. Let it send

3. Change event

4. Notice that the message is still there, marked as sent

New behaviour

Steps to validate that it works:

1. Create event (unpublished)

2. No scheduled messages

--

1. Create event

2. Let it send

3. Change event

4. Notice that the message is still there, but a new one was added as well