split checkPrecondition so it can be used in cleaner as well

src/storage/interface.js

@@ -12,7 +12,8 @@
 //     them to tune the concurrency based on failures/rate limits accordingly
 exports = module.exports = {
     getBackupRootPath,
-    checkBackupPreconditions,
+    getBackupProviderStatus,
+    getAvailableSize,
 
     upload,
 
@@ -34,8 +35,7 @@ exports = module.exports = {
 };
 
 const assert = require('assert'),
-    BoxError = require('../boxerror.js'),
-    DataLayout = require('../datalayout.js');
+    BoxError = require('../boxerror.js');
 
 function removePrivateFields(apiConfig) {
     // in-place removal of tokens and api keys with constants.SECRET_PLACEHOLDER
@@ -54,9 +54,16 @@ function getBackupRootPath(apiConfig) {
     return '/';
 }
 
-async function checkBackupPreconditions(apiConfig, dataLayout) {
+async function getBackupProviderStatus(apiConfig) {
     assert.strictEqual(typeof apiConfig, 'object');
-    assert(dataLayout instanceof DataLayout, 'dataLayout must be a DataLayout');
+
+    return { state: 'active' };
+}
+
+async function getAvailableSize(apiConfig) {
+    assert.strictEqual(typeof apiConfig, 'object');
+
+    return Number.POSITIVE_INFINITY;
 }
 
 function upload(apiConfig, backupFilePath, sourceStream, callback) {