Gitlab Geo: Registry Sync activation

Toe enable Docker registry synchronisation you write in your docs one should do:

gitlab_rails['geo_registry_replication_enabled'] = true
gitlab_rails['geo_registry_replication_primary_api_url'] = 'https://primary.example.com:5050/' # Primary registry address, it will be used by the secondary node to directly communicate to primary registry

well this cannot be done in the chart. as far as i can see, this setting will set the following properties in the gitlab.yml.erb:

geo:
  node_name: <%= @geo_node_name %>
  registry_replication:
    enabled: <%= @geo_registry_replication_enabled %>
    primary_api_url: <%= @geo_registry_replication_primary_api_url %>

but how do i set these values in the chart? the configuration of the file is created by the _geo.tpl which only has the geo.config macro as defined:

{{- define "gitlab.geo.config" -}}
{{- if .Values.global.geo.enabled -}}
geo:
  node_name: {{ default "" .Values.global.geo.nodeName }}
{{- end -}}
{{- end -}}

i cannot see how to enable the registry_replication, perhaps there is some undocumented feature in the chart which i don't know?

thanks