create a private key.
$ openssl genrsa -out vivek.key 2048

create a certificate signing request (CSR). CN is the username and O the group.
$ openssl req -new -key vivek.key -out vivek.csr -subj "/CN=vivek/O=developers"

sign the CSR with the Kubernetes CA.
$ openssl x509 -req -in vivek.csr -CA /etc/kubernetes/pki/ca.crt -CAkey /etc/kubernetes/pki/ca.key -CAcreateserial -out vivek.crt -days 20

create the user inside Kubernetes.
$ kubectl config set-credentials vivek --client-certificate vivek.crt --client-key vivek.key

create a context for the user.
$ kubectl config set-context vivek-kindkind --cluster kind-kind --user vivek
