event type fix and better AWS bounce setup instructions

[mikob]

AWS notifications look like this:

{
  "Type" : "Notification",
  "MessageId" : "cd358678-b3e1-5281-9881-d0e35abe0a4c",
  "TopicArn" : "arn:aws:sns:us-west-(redacted):bounces_and_complaints",
  "Subject" : "Amazon SES Email Event Notification",
  "Message" : "{\"eventType\":\"Bounce\",
    \"bounce\":{
...

So this fixes the view code to look at the right property.

[pcraciunoiu]

@mikob thanks for your contribution! This looks promising, however the tests/build fails. Could you fix?

[pcraciunoiu]

LGTM, will merge this and make a release

[znotdead]

How do you have 'eventType'?
Mine response is notificationType
From response message is: {'notificationType': 'Bounce', ...
According to doc it's not true too. https://docs.aws.amazon.com/ses/latest/DeveloperGuide/notification-contents.html#top-level-json-object
So using django-ses I get warning in logs Received unknown event

[mrbaboon]

@znotdead 👍