Support mTLS for LDAP configuration

[mhoshi-vm]

Is your feature request related to a problem? Please describe.

Currently we only support one way TLS verification with password authentication.
However (although still rare) LDAP does support mTLS configuration.

https://ltb-project.org/documentation/openldap_ssl_tls_mutual_authentication.html

Dex has this configured so this will be a hurdle for customers to migrate out of it

dexidp/dex#1277

Describe the solution you'd like

for TLSSpec there should be a field for client certificate and key.

Describe alternatives you've considered

No alternative if the LDAP server only accepts mTLS

[cfryanr]

@mhoshi-vm Is this a duplicate of #1425, or do you see some difference in your needs versus what is described in that other issue?

[cfryanr]

Thanks for creating this issue @mhoshi-vm. I didn't hear back from you, so I'm going to assume that this is a duplicate of #1425. Please let us know if there are any differences in what you were requesting, and we can reopen this issue.