operator: add a limits route to determine max app resource limits

src/apps.js

@@ -79,6 +79,7 @@ exports = module.exports = {
     getDataDir,
     getIcon,
     getMemoryLimit,
+    getLimits,
 
     listEventlog,
 
@@ -160,6 +161,7 @@ const appstore = require('./appstore.js'),
     spawn = require('child_process').spawn,
     split = require('split'),
     superagent = require('superagent'),
+    system = require('./system.js'),
     tasks = require('./tasks.js'),
     TransformStream = require('stream').Transform,
     users = require('./users.js'),
@@ -468,6 +470,14 @@ async function getIcon(app, options) {
     return null;
 }
 
+async function getLimits(app) {
+    assert.strictEqual(typeof app, 'object');
+
+    return {
+        memory: await system.getMemory()
+    };
+}
+
 function getMemoryLimit(app) {
     assert.strictEqual(typeof app, 'object');