Fix for new pagination envelope in Metabase 0.40.0

[gouline]

Since Metabase 0.40.0, API responses are encapsulated in:

{
    "data": [ "OLD RESPONSE HERE" ],
    "limit": 50,
    "offset": 0,
    "total": 2
}

This change checks if "data" key is present in the root and uses that instead. I will revisit this later, if I need to cater for pagination issues in requests.

[gouline]

This change has been backported and released as 0.7.1 to unblock anyone who upgraded their Metabase, but not ready to migrate to 0.8.0 to be released soon with some breaking changes.

[fernandobrito]

Thanks for the good PR description. One of our in-house automation (deactivate inactive Metabase users) started failing after upgrading to 0.40 and your description here made it very easy to understand exactly what has changed 😄 .