Add NullCacheAdapter (#2636)

* Add NullCacheAdapter

* clear returns promise explicitly

* Add NullCacheAdapter accessor

src/Adapters/Cache/NullCacheAdapter.js

@@ -0,0 +1,25 @@
+export class NullCacheAdapter {
+
+  constructor(ctx) {
+  }
+
+  get(key) {
+    return new Promise((resolve, _) => {
+      return resolve(null);
+    })
+  }
+
+  put(key, value, ttl) {
+    return Promise.resolve();
+  }
+
+  del(key) {
+    return Promise.resolve();
+  }
+
+  clear() {
+    return Promise.resolve();
+  }
+}
+
+export default NullCacheAdapter;

src/index.js

@@ -2,6 +2,7 @@ import ParseServer          from './ParseServer';
 import S3Adapter            from 'parse-server-s3-adapter'
 import FileSystemAdapter    from 'parse-server-fs-adapter'
 import InMemoryCacheAdapter from './Adapters/Cache/InMemoryCacheAdapter'
+import NullCacheAdapter     from './Adapters/Cache/NullCacheAdapter'
 import TestUtils            from './TestUtils';
 import { useExternal }      from './deprecated';
 import { getLogger }        from './logger';
@@ -21,4 +22,4 @@ Object.defineProperty(module.exports, 'logger', {
 });
 
 export default ParseServer;
-export { S3Adapter, GCSAdapter, FileSystemAdapter, InMemoryCacheAdapter, TestUtils, _ParseServer as ParseServer };
+export { S3Adapter, GCSAdapter, FileSystemAdapter, InMemoryCacheAdapter, NullCacheAdapter, TestUtils, _ParseServer as ParseServer };