add CDN config option

i18n/en.i18n.json

@@ -197,6 +197,7 @@
   "FileUpload_S3_AWSAccessKeyId" : "Amazon S3 AWSAccessKeyId",
   "FileUpload_S3_AWSSecretAccessKey" : "Amazon S3 AWSSecretAccessKey",
   "FileUpload_S3_Bucket" : "Amazon S3 bucket name",
+  "FileUpload_S3_CDN" : "CDN domain",
   "FileUpload_Storage_Type" : "Storage Type",
   "Follow_social_profiles" : "Follow our social profiles, fork us on github and share your thoughts about the rocket.chat app on our trello board.",
   "Force_SSL" : "Force SSL",

packages/rocketchat-file-upload/server/configS3.js

@@ -6,6 +6,7 @@ createS3Directive = _.debounce(() => {
 	var acl = RocketChat.settings.get('FileUpload_S3_Acl');
 	var accessKey = RocketChat.settings.get('FileUpload_S3_AWSAccessKeyId');
 	var secretKey = RocketChat.settings.get('FileUpload_S3_AWSSecretAccessKey');
+	var cdn = RocketChat.settings.get('FileUpload_S3_CDN');
 
 	if (type === 'AmazonS3' && !_.isEmpty(bucket) && !_.isEmpty(accessKey) && !_.isEmpty(secretKey)) {
 		if (Slingshot._directives[directiveName]) {
@@ -26,6 +27,10 @@ createS3Directive = _.debounce(() => {
 			config.acl = acl;
 		}
 
+		if (!_.isEmpty(cdn)) {
+			config.cdn = cdn;
+		}
+
 		Slingshot.createDirective(directiveName, Slingshot.S3Storage, config);
 	} else {
 		if (Slingshot._directives[directiveName]) {
@@ -53,3 +58,7 @@ RocketChat.settings.get('FileUpload_S3_AWSAccessKeyId', function(settingKey, set
 RocketChat.settings.get('FileUpload_S3_AWSSecretAccessKey', function(settingKey, settingValue) {
 	createS3Directive();
 });
+
+RocketChat.settings.get('FileUpload_S3_CDN', function(settingKey, settingValue) {
+	createS3Directive();
+});

packages/rocketchat-file-upload/server/startup/settings.js

@@ -48,5 +48,14 @@ Meteor.startup(function() {
 			value: 'AmazonS3'
 		}
 	});
+	RocketChat.settings.add('FileUpload_S3_CDN', '', {
+		group: 'FileUpload',
+		section: 'Amazon S3',
+		type: 'string',
+		enableQuery: {
+			_id: 'FileUpload_Storage_Type',
+			value: 'AmazonS3'
+		}
+	});
 });