command missing in new Temporal CLI

Is your feature request related to a problem? Please describe.
I have not found a command replacing this behaviour in the new cli, where you update a namespace to contain multiple clusters:
tctl --namespace "myNamespace" namespace update --clusters clusterA clusterB

for context: https://community.temporal.io/t/running-into-problems-testing-multi-cluster-replication-locally-via-docker/5920/8

it is marked as the solution in thread above.

Describe the solution you'd like
temporal operator namespace update --cluster 'clusterA clusterB' "myNamespace"
Have the cluster accept a list of clusters and not only a single one.

Describe alternatives you've considered

1. Use the old tctl, but at some point it will be deprecated.

2. I cannot create it from scratch since we already have namespaces in use.

Start at the Temporal CLI entry point for temporal operator namespace update and inspect how the --cluster option is parsed and passed to the namespace update operation. Done means an existing namespace can be updated with multiple cluster names, matching the old tctl behavior; add or update coverage for that command if the entry point has tests.