Mariadb: Add security context for mysql exporter pod/container

This adds a security context to the mysql prometheus exporter pod,
which changes the user from root to the nobody user (uid 99 here)
instead

This also adds the container security context to explicitly set
allowPrivilegeEscalation to false

Change-Id: I5ddebb059e3c31c231fdc4c24190a65f23e37785

mariadb/templates/monitoring/prometheus/exporter-deployment.yaml

@@ -38,6 +38,7 @@ spec:
 {{ tuple $envAll "prometheus_mysql_exporter" "exporter" | include "helm-toolkit.snippets.kubernetes_metadata_labels" | indent 8 }}
       namespace: {{ .Values.endpoints.prometheus_mysql_exporter.namespace }}
     spec:
+{{ dict "envAll" $envAll "application" "mysql_exporter" | include "helm-toolkit.snippets.kubernetes_pod_security_context" | indent 6 }}
       shareProcessNamespace: true
       serviceAccountName: {{ $serviceAccountName }}
       nodeSelector:
@@ -49,6 +50,8 @@ spec:
         - name: mysql-exporter
 {{ tuple $envAll "prometheus_mysql_exporter" | include "helm-toolkit.snippets.image" | indent 10 }}
 {{ tuple $envAll $envAll.Values.pod.resources.prometheus_mysql_exporter | include "helm-toolkit.snippets.kubernetes_resources" | indent 10 }}
+          securityContext:
+            allowPrivilegeEscalation: false
           command:
             - /tmp/mysqld-exporter.sh
             - start

mariadb/values.yaml

@@ -51,6 +51,9 @@ labels:
     node_selector_value: enabled
 
 pod:
+  user:
+    mysql_exporter:
+      uid: 99
   affinity:
     anti:
       type: