Fix logic to cater for missing and additional cloudtrail fields

[marjamis]

In tests/example_cloud_trails.json cater for the ability for fields to be missing (or additional) without generating errors. Currently there are placeholders of:

"eventName": "This doesn't exist and needs to be catered for in my code and removed from this test",
"userAgent": "This doesn't exist and needs to be catered for in my code and removed from this test",
"eventSource": "This doesn't exist and needs to be catered for in my code and removed from this test",

to remove the errors. These should also be removed from the test data to get it up and running.