clustermesh: Validate cluster-id value as per requirement

This commit is to make sure that cluster-id is numeric and within range
of 1-255.

https://docs.cilium.io/en/stable/gettingstarted/clustermesh/clustermesh/#gs-clustermesh

Fixes: #143

Co-authored-by: Tobias Klauser <tobias.klauser@gmail.com>
Signed-off-by: Tam Mach <tam.mach@cilium.io>

clustermesh/clustermesh.go

@@ -905,6 +905,15 @@ func (k *K8sClusterMesh) Connect(ctx context.Context) error {
 			aiLocal.ClusterName, aiLocal.ClusterID)
 	}
 
+	cid, err := strconv.Atoi(aiRemote.ClusterID)
+	if err != nil {
+		return fmt.Errorf("local cluster has non-numeric cluster ID %s. Only numeric values 1-255 are allowed", aiRemote.ClusterID)
+	}
+	if cid > 255 || cid < 1 {
+		return fmt.Errorf("remote cluster has the cluster ID out of acceptable range (e.g. 1-255) (cluster ID: %d)",
+			cid)
+	}
+
 	if aiRemote.ClusterName == aiLocal.ClusterName {
 		return fmt.Errorf("remote and local cluster have the same, non-unique name: %s", aiLocal.ClusterName)
 	}