Add AWS creds in testing example

[hakbailey]

Such as: https://github.com/MITLibraries/workflow/blob/a20d9dc40a73959da3b1cf1915fa390721c59e61/tests/conftest.py#L13-L18

Just so we have it documented here for reference

[JPrevost]

If I'm not mistaken, what we may want here is an explanation on how we commonly mock AWS in testing and / or development environments (aka Moto).

That link example is mostly a side effect of using mocked services.

Regardless, a "how we are Mocking AWS calls in testing and sometimes development" would be 🌈 .