bug#47788: Add support for TLS client certificates to 'erc-tls'

[Robert Pluim]

>>>>> On Thu, 15 Apr 2021 00:16:38 -0400, Amin Bandali <bandali@gnu.org> said:

    Amin> Tags: patch
    Amin> After a few recent changes in my IRC/ERC setup, I felt ERC's lack of
    Amin> support for connecting to IRC networks using TLS client certificates 
as
    Amin> an alternative to traditional password-based authentication.  So I 
spent
    Amin> some time a few nights ago and wired things up in ERC to allow 
passing a
    Amin> client certificate to `open-network-stream'.

It would be nice if you could arrange for an option to pass
':client-certificate t' to 'open-network-stream' so it would leverage
'auth-source'

Robert