API docs: https://nickray.github.io/pkcs11-uri/pkcs11_uri/
One way to generate URIs to feed into this library is the p11tool
in GnuTLS.
Running p11tool --list-tokens
returns the URIs for all available tokens.
Running p11tool --list-all <token URI>
then lists all the objects in that token.
For private keys, use GNUTLS_PIN=<pin> p11tool --login --list-all <token URI>
.