Add --tls-sans flag to k3kcli (#925)

* Add --tls-sans flag to k3kcli cluster create

* Refine --tls-sans flag description in k3kcli documentation

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* Fix TLS SANs handling in cluster creation by using hostname directly

* Implement extractHost function and update TLS SAN handling in cluster creation

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

docs/cli/k3kcli.adoc

@@ -65,6 +65,7 @@ k3kcli cluster create [command options] NAME
       --storage-class-name string     storage class name for dynamic persistence type
       --storage-request-size string   storage size for dynamic persistence type
       --timeout duration              The timeout for waiting for the cluster to become ready (e.g., 10s, 5m, 1h). (default 3m0s)
+      --tls-sans strings              additional Subject Alternative Names for the cluster server TLS certificate
       --token string                  token of the cluster
       --version string                k3s version
 ----

docs/cli/k3kcli_cluster_create.md

@@ -36,6 +36,7 @@ k3kcli cluster create [command options] NAME
       --storage-class-name string     storage class name for dynamic persistence type
       --storage-request-size string   storage size for dynamic persistence type
       --timeout duration              The timeout for waiting for the cluster to become ready (e.g., 10s, 5m, 1h). (default 3m0s)
+      --tls-sans strings              additional Subject Alternative Names for the cluster server TLS certificate
       --token string                  token of the cluster
       --version string                k3s version
 ```