@ReadOperation
    @Operation(summary = "Get registered and authorized devices for the principal", parameters = @Parameter(name = "principal", required = true, description = "The principal to look up"))
    public Collection<String> devices(@Selector final String principal) {
        return repository.getObject().getAuthorizedDevicesFor(principal);
    }
Devices collection.

@param principal the principal
@return the collection
support/cas-server-support-qr-authentication/src/main/java/org/apereo/cas/qr/web/QRAuthenticationDeviceRepositoryEndpoint.java