A server-stored device credential used for authentication.
.. attribute:: public_key
A public key used to verify the signature of
JSON Web Tokens (JWTs). When adding a new device
credential, either via device creation or via
modifications, this public key credential may be
required to be signed by one of the registry
level certificates. More specifically, if the
registry contains at least one certificate, any
new device credential must be signed by one of
the registry certificates. As a result, when the
registry contains certificates, only X.509
certificates are accepted as device credentials.
However, if the registry does not contain a
certificate, self-signed certificates and public
keys will be accepted. New device credentials
must be different from every registry-level
expiration_time [Optional] The time at which this credential becomes
invalid. This credential will be ignored for new client
authentication requests after this timestamp; however, it
will not be automatically deleted.