add provider specific removePrivateFields to redact tokens and secrets

src/dns/digitalocean.js

@@ -1,6 +1,7 @@
 'use strict';
 
 exports = module.exports = {
+    removePrivateFields: removePrivateFields,
     upsert: upsert,
     get: get,
     del: del,
@@ -25,6 +26,11 @@ function formatError(response) {
     return util.format('DigitalOcean DNS error [%s] %j', response.statusCode, response.body);
 }
 
+function removePrivateFields(domainObject) {
+    domainObject.config.token = domains.SECRET_PLACEHOLDER;
+    return domainObject;
+}
+
 function getInternal(dnsConfig, zoneName, name, type, callback) {
     assert.strictEqual(typeof dnsConfig, 'object');
     assert.strictEqual(typeof zoneName, 'string');