sftp: prefix the id with app- and volume-

this helps the backend identify the type of mount

src/routes/filemanager.js

@@ -1,7 +1,8 @@
 'use strict';
 
 exports = module.exports = {
-    proxy
+    proxyAppData,
+    proxyVolumeData
 };
 
 const assert = require('assert'),
@@ -12,10 +13,8 @@ const assert = require('assert'),
     services = require('../services.js'),
     url = require('url');
 
-async function proxy(req, res, next) {
-    assert.strictEqual(typeof req.params.id, 'string');
-
-    const id = req.params.id; // app id or volume id
+async function proxy(id, req, res, next) {
+    assert.strictEqual(typeof id, 'string');
 
     req.clearTimeout();
 
@@ -40,3 +39,11 @@ async function proxy(req, res, next) {
         next(new HttpError(500, error));
     });
 }
+
+function proxyAppData(req, res, next) {
+    proxy(`app-${req.params.id}`, req, res, next);
+}
+
+function proxyVolumeData(req, res, next) {
+    proxy(`volume-${req.params.id}`, req, res, next);
+}