Allow multiple values for subject fields

[lstellway]

Is your feature request related to a problem? Please describe.
While going through Kubernetes documentation to learn how to authenticate a user using a PKI key pair, they mention that to add a user to multiple groups, you can set multiple Organization values in the Subject certificate signing request.

There is currently not a way to do this with the current setup.

Describe the solution you'd like
We need a solution for specifying multiple values on these fields.