feat: keep GatewayClass on uninstall via helm.sh/resource-policy when it's the default (#1283)

Signed-off-by: Md. Istiak <mdistiak@appscode.com>
Signed-off-by: Arnob kumar saha <arnob@appscode.com>
Co-authored-by: Arnob kumar saha <arnob@appscode.com>

Author: Istiak2019331114

charts/service-gateway/templates/gateway/gwclass.yaml

@@ -12,6 +12,9 @@ metadata:
     {{- with .Values.gatewayClass.annotations }}
       {{- toYaml . | nindent 4 }}
     {{- end }}
+    {{- if eq (dig "catalog.appscode.com/is-default-gatewayclass" "" (.Values.gatewayClass.annotations | default dict)) "true" }}
+    helm.sh/resource-policy: keep
+    {{- end }}
 spec:
   controllerName: {{ .Values.gateway.config.envoyGateway.gateway.controllerName }}
   {{- with .Values.gatewayClass.description }}