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

src/routes/apps.js

@@ -48,6 +48,8 @@ exports = module.exports = {
     uploadFile,
     downloadFile,
 
+    getLimits,
+
     load
 };
 
@@ -837,3 +839,12 @@ async function getTask(req, res, next) {
 
     next(new HttpSuccess(200, result));
 }
+
+async function getLimits(req, res, next) {
+    assert.strictEqual(typeof req.app, 'object');
+
+    const [error, limits] = await safe(apps.getLimits(req.app));
+    if (error) return next(BoxError.toHttpError(error));
+
+    next(new HttpSuccess(200, { limits }));
+}