[stable/2023.1] fix: add CA mounts in the Prometheus oauth2 container (#1334)

This is an automated cherry-pick of #1329
/assign mnaser
diff --git a/roles/kube_prometheus_stack/vars/main.yml b/roles/kube_prometheus_stack/vars/main.yml
index e638d22..4cf2386 100644
--- a/roles/kube_prometheus_stack/vars/main.yml
+++ b/roles/kube_prometheus_stack/vars/main.yml
@@ -133,6 +133,14 @@
             - containerPort: 8082
               name: oauth2-metrics
               protocol: TCP
+          volumeMounts:
+            - name: ca-certificates
+              mountPath: /etc/ssl/certs/ca-certificates.crt
+              readOnly: true
+      volumes:
+        - name: ca-certificates
+          hostPath:
+            path: "{{ defaults_ca_certificates_path }}"
   grafana:
     adminPassword: "{{ kube_prometheus_stack_grafana_admin_password }}"
     extraSecretMounts:
@@ -342,6 +350,14 @@
             - containerPort: 8082
               name: oauth2-metrics
               protocol: TCP
+          volumeMounts:
+            - name: ca-certificates
+              mountPath: /etc/ssl/certs/ca-certificates.crt
+              readOnly: true
+      volumes:
+        - name: ca-certificates
+          hostPath:
+            path: "{{ defaults_ca_certificates_path }}"
     additionalServiceMonitors:
       - name: ceph
         jobLabel: application