add a supergraph configmap option to the helm chart (#2119)

Here's an example of values.yaml that you could use to mount this to
your container:

```
extraEnvVars:
  - name: APOLLO_ROUTER_SUPERGRAPH_PATH
    value: /data/supergraph-schema.graphql

extraVolumeMounts:
  - name: supergraph-schema
    mountPath: /data
    readOnly: true

extraVolumes:
  - name: supergraph-schema
    configMap:
      name: "{{ .Release.Name }}-supergraph"
      items:
        - key: supergraph-schema.graphql
          path: supergraph-schema.graphql

```

Note: This takes advantage of the fact that we `tpl` template the
extraVolumes in the deployment template, so {{ .Release.Name }} will be
templated into the release name at install. You don't have to do this,
you could just hard-code it, but this is neater.

Here's an example command line:

```
helm upgrade --install --create-namespace --namespace router-test --set-file supergraphFile=supergraph-schema.graphql router-test oci://ghcr.io/apollographql/helm-charts/router --version 1.0.0-rc.9 --values values.yaml
```

NB: rc.9 doesn't exist, so the command is purely illustrative to show
how this works.

NEXT_CHANGELOG.md

@@ -26,6 +26,38 @@ By [@USERNAME](https://github.com/USERNAME) in https://github.com/apollographql/
 # [x.x.x] (unreleased) - 2022-mm-dd
 ## ❗ BREAKING ❗
 ## 🚀 Features
+
+### Add a supergraph configmap option to the helm chart ([PR #2119](https://github.com/apollographql/router/pull/2119))
+
+Adds the capability to create a configmap containing your supergraph schema. Here's an example of how you could make use of this from your values.yaml and with the `helm` install command.
+
+```yaml
+extraEnvVars:
+  - name: APOLLO_ROUTER_SUPERGRAPH_PATH
+    value: /data/supergraph-schema.graphql
+
+extraVolumeMounts:
+  - name: supergraph-schema
+    mountPath: /data
+    readOnly: true
+
+extraVolumes:
+  - name: supergraph-schema
+    configMap:
+      name: "{{ .Release.Name }}-supergraph"
+      items:
+        - key: supergraph-schema.graphql
+          path: supergraph-schema.graphql
+```
+
+With that values.yaml content, and with your supergraph schema in a file name supergraph-schema.graphql, you can execute:
+
+```
+helm upgrade --install --create-namespace --namespace router-test --set-file supergraphFile=supergraph-schema.graphql router-test oci://ghcr.io/apollographql/helm-charts/router --version 1.0.0-rc.9 --values values.yaml
+```
+
+By [@garypen](https://github.com/garypen) in https://github.com/apollographql/router/pull/2119
+
 ## 🐛 Fixes
 ## 🛠 Maintenance
 ## 📚 Documentation

helm/chart/router/templates/supergraph-cm.yaml

@@ -0,0 +1,12 @@
+{{- if .Values.supergraphFile }}
+{{- $routerFullName := include "router.fullname" .  -}}
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: {{ $routerFullName }}-supergraph
+  labels:
+    {{- include "router.labels" . | nindent 4 }}
+data:
+  supergraph-schema.graphql: |-
+{{ .Values.supergraphFile | indent 4 }}
+{{- end }}

helm/chart/router/values.yaml

@@ -30,6 +30,10 @@ managedFederation:
   # -- If using managed federation, the variant of which graph to use
   graphRef: ""
 
+# This should not be specified in values.yaml. It's much simpler to use --set-file from helm command line.
+# e.g.: helm ... --set-file supergraphFile="location of your supergraph file"
+supergraphFile:
+
 # An array of extra environmental variables
 # Example:
 # extraEnvVars: