Add functionality to grab FileVault Recovery Key for devices

[malcolmaa]

It would be nice to have the Filevault Recovery Key also available to be synced to the asset in Snipe.

We currently check the entries manually in Kandji or cross-reference a Device Secrets report

The API key would have to be updated to include Device Secrets > Filevault recovery key, but it'd eliminate a lot of steps if it's possible to be implemented in the existing script.