feat(argocd-image-updater): Optionally expose metrics (#1005)

* feat(argocd-image-updater): Optionally expose metrics

Signed-off-by: Jan Pieper <kontakt@jan-pieper.info>

* Apply suggestions from code review

Signed-off-by: Marco Kilchhofer <mkilchhofer@users.noreply.github.com>

* Add missing link references to README

Signed-off-by: Marco Kilchhofer <mkilchhofer@users.noreply.github.com>

Co-authored-by: Marco Kilchhofer <mkilchhofer@users.noreply.github.com>

charts/argocd-image-updater/templates/deployment.yaml

@@ -60,6 +60,11 @@ spec:
           imagePullPolicy: {{ .Values.image.pullPolicy }}
           ports:
             - containerPort: 8080
+            {{ if .Values.metrics.enabled }}
+            - name: metrics
+              containerPort: 8081
+              protocol: TCP
+            {{- end }}
           readinessProbe:
             httpGet:
               path: /healthz