Provisioning: Go template variables stripped when using __file provider in Docker Compose

### What happened? I am using configuration files to provision Grafana. I have a slack alert contact point defined like : ```.yml contactPoints: - orgId: 1 name: Webhook receivers: - uid: webhook type: slack settings: title: '${ALERT_TITLE_TEMPLATE_PATH}' text: '${ALERT_TEXT_TEMPLATE_PATH}' disableResolveMessage: false ``` The variable `ALERT_TITLE_TEMPLATE_PATH` is passed in the docker compose. The variable itself points to a file provider variable in the docker compose. ```.yml grafana: environment: - ALERT_TITLE_TEMPLATE_PATH=$$__file{/var/lib/grafana/notification-templates/title.go.tmpl} - ALERT_TEXT_TEMPLATE_PATH=$$__file{/var/lib/grafana/notification-templates/body.go.tmpl} volumes: - ./notification-templates:/var/lib/grafana/notification-templates ``` notification-templates/body.go.tmpl ```go.tmpl {{ define "__text_values_list" -}} {{- if len .Values -}} {{ $first := true }} {{- range $refID, $value := .Values -}} {{- if $first -}} {{ $first = false }} {{- else -}} {{ "\n" }} {{- end -}} {{- $refID }} = {{ $value -}} {{- end -}} {{- else -}} [no value] {{- end -}} {{ end }} {{ template "__text_values_list" .}} ``` This setup works except that the variables are missing from the template which is loaded into Grafana. ```.go.tmpl {{ define "__text_values_list" -}} {{- if len .Values -}} {{ := true }} {{- range , := .Values -}} {{- if -}} {{ = false }} {{- else -}} {{ "\n" }} {{- end -}} {{- }} = {{ -}} {{- end -}} {{- else -}} [no value] {{- end -}} {{ end }} {{ template "__text_values_list" .}} ``` I tried by escaping the variables, like `$$first`, but then the variable changed to `first` instead of `$first` ```go.tmpl {{ …