Log CN of client cert that authenticates with ledger. Document requirements around cert format and any checks done on cert

[nycnewman]

When Mutual TLS enabled, it would be good to have:

• details of client logged for audit purposes
• documentation on any mandatory requirements around cert formats (i.e. PKCS8 instead of PKCS1)
• documentation on what checks are made on certs (server or client) around revocation (CRL or OCSP) by server, any cert attributes, etc
• documentation on what, if any, linkage between client cert and authentication, authorization decisions within Ledger