Fires once for each key when listing keys.
The 'callback' is called when the 'KeyList' event is emited.
The argument 'e' has the following properties:
e.name e.purpose e.creationDate e.primaryVersion
Name reflects the name of the key.
Purpose reflects the key's purpose. Possible values are:
- 0: Unspecified.
- 1: A symmetric key used for encryption and decryption.
- 2: An asymmetric key used for signing and verification.
- 3: An asymmetric key used for encryption and decryption.
CreationDate reflects the key's creation date, formatted as an RFC 3339 UTC timestamp.
PrimaryVersion reflects the Id of the key's primary version if it is symmetric. For asymmetric keys, it is always empty, since asymmetric keys cannot have a primary version.