fails when deployed in controller model

I got the following traceback when I did a deployment in the controller model of my microk8s-hosted controller.

Usually when you bootstrap on IAAS you get a `default` model as well as `controller` and are switched to the former, but apparently not on CAAS.

The `controller` model appears to be unique in that, unlike other models, the k8s namespace is not simply the name of the model but e.g. `controller-microk8s-localhost`.

unit-mattermost-ingress-0: 11:44:52 ERROR unit.mattermost-ingress/0.juju-log Uncaught exception while in charm code:
Traceback (most recent call last):
  File "./src/charm.py", line 430, in <module>
    main(NginxIngressCharm)
  File "/var/lib/juju/agents/unit-mattermost-ingress-0/charm/venv/ops/main.py", line 406, in main
    _emit_charm_event(charm, dispatcher.event_name)
  File "/var/lib/juju/agents/unit-mattermost-ingress-0/charm/venv/ops/main.py", line 140, in _emit_charm_event
    event_to_emit.emit(*args, **kwargs)
  File "/var/lib/juju/agents/unit-mattermost-ingress-0/charm/venv/ops/framework.py", line 278, in emit
    framework._emit(event)
  File "/var/lib/juju/agents/unit-mattermost-ingress-0/charm/venv/ops/framework.py", line 722, in _emit
    self._reemit(event_path)
  File "/var/lib/juju/agents/unit-mattermost-ingress-0/charm/venv/ops/framework.py", line 767, in _reemit
    custom_handler(event)
  File "./src/charm.py", line 405, in _on_config_changed
    self._define_service()
  File "./src/charm.py", line 330, in _define_service
    api.create_namespaced_service(
  File "/var/lib/juju/agents/unit-mattermost-ingress-0/charm/venv/kubernetes/client/api/core_v1_api.py", line 8304, in create_namespaced_service
    return self.create_namespaced_service_with_http_info(namespace, body, **kwargs) # noqa: E501
  File "/var/lib/juju/agents/unit-mattermost-ingress-0/charm/venv/kubernetes/client/api/core_v1_api.py", line 8399, in create_namespaced_service_with_http_info
    return self.api_client.call_api(
  File "/var/lib/juju/agents/unit-mattermost-ingress-0/charm/venv/kubernetes/client/api_client.py", line 348, in call_api
    return self.__call_api(resource_path, method,
  File "/var/lib/juju/agents/unit-mattermost-ingress-0/charm/venv/kubernetes/client/api_client.py", line 180, in __call_api
    response_data = self.request(
  File "/var/lib/juju/agents/unit-mattermost-ingress-0/charm/venv/kubernetes/client/api_client.py", line 391, in request
    return self.rest_client.POST(url,
  File "/var/lib/juju/agents/unit-mattermost-ingress-0/charm/venv/kubernetes/client/rest.py", line 274, in POST
    return self.request("POST", url,
  File "/var/lib/juju/agents/unit-mattermost-ingress-0/charm/venv/kubernetes/client/rest.py", line 233, in request
    raise ApiException(http_resp=r)
kubernetes.client.exceptions.ApiException: (404)
Reason: Not Found
HTTP response headers: HTTPHeaderDict({'Cache-Control': 'no-cache, private', 'Content-Type': 'application/json', 'X-Kubernetes-Pf-Flowschema-Uid': '57360413-dd7d-4ac6-8521-1eb077bd5896', 'X-Kubernetes-Pf-Prioritylevel-Uid': '584d7d24-3cbd-4ef6-8917-d9ce2bb79b62', 'Date': 'Sun, 13 Jun 2021 23:44:52 GMT', 'Content-Length': '200'})
HTTP response body: {"kind":"Status","apiVersion":"v1","metadata":{},"status":"Failure","message":"namespaces \"controller\" not found","reason":"NotFound","details":{"name":"controller","kind":"namespaces"},"code":404}

unit-mattermost-ingress-0: 11:44:53 ERROR juju.worker.uniter.operation hook "config-changed" (via hook dispatching script: dispatch) failed: exit status 1