decodeBodyMap fails for newly created AutomationToken

[dimiechatz]

The creation of an AutomationToken using CreateAutomationToken is failing with:

* error decoding 'last_used_at': parsing time "" as "2006-01-02 15:04:05": cannot parse "" as "2006"

The AutomationToken is actually being created but not being returned because of the error returned by decodeBodyMap.
It should be expected for the value of last_used_at to be an empty string after the creation a token.

The error is returned initially from stringToTimeHookFunc(): https://github.com/fastly/go-fastly/blob/v9.12.0/fastly/client.go#L743

[kpfleming]

Thanks for the detailed report.