Fix LDAP Smartcard subject formatting

What does this MR do and why?

Fix LDAP Smartcard subject formatting

Fixes LDAP smartcard subject to be formatted with , instead of / as in the raw certificate subject info.

Co-authored-by: @ParkerMc

References

• #554639 (closed)
• Rollout issue: #577375

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Before	After

How to set up and validate locally

This is difficult to test locally due to requiring an ActiveDirectory LDAP server for GitLab to connect to, and certificates with complicated subject names rather than the usual email addresses. Please check the spec coverage to see what is changing.

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Related to #554639 (closed)