Comment 2 for bug 2058095

WE also have the same issue
unit-kubernetes-control-plane-1: 19:58:46 ERROR unit.kubernetes-control-plane/1.juju-log 'str' object does not support item assignment
Traceback (most recent call last):
  File "/var/lib/juju/agents/unit-kubernetes-control-plane-1/charm/venv/charms/reconciler.py", line 34, in reconcile
    result = self.reconcile_function(event)
  File "/var/lib/juju/agents/unit-kubernetes-control-plane-1/charm/./src/charm.py", line 499, in reconcile
    self.request_certificates()
  File "/var/lib/juju/agents/unit-kubernetes-control-plane-1/charm/./src/charm.py", line 592, in request_certificates
    self.certificates.request_server_cert(cn=common_name, sans=sans)
  File "/var/lib/juju/agents/unit-kubernetes-control-plane-1/charm/venv/ops/interface_tls_certificates/requires.py", line 160, in request_server_cert
    requests[cn] = {"sans": sans or []}
TypeError: 'str' object does not support item assignment

This also affects the control plane and all workers
the same patch works
```
requests = data.get("cert_requests", {})
import json
requests = json.loads(requests)
requests[cn] = {"sans": sans or []}
data["cert_requests"] = json.dumps(requests)
```