Move sign-in sheet under fb folder

Summary: SignInSheet and "dispatcher/user" are not used in public build, so it doesn't make sense to keep them on github.

Reviewed By: passy

Differential Revision: D28789384

fbshipit-source-id: aa1ab0fc70f2211260017be42762714b753ea877

desktop/app/src/dispatcher/fb-stubs/user.tsx

@@ -0,0 +1,12 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+export default () => {
+  // no public implementation
+};

desktop/app/src/dispatcher/index.tsx

@@ -17,7 +17,7 @@ import tracking from './tracking';
 import server from './server';
 import notifications from './notifications';
 import plugins from './plugins';
-import user from './user';
+import user from './fb-stubs/user';
 import pluginManager from './pluginManager';
 import reactNative from './reactNative';
 import pluginMarketplace from './fb-stubs/pluginMarketplace';

desktop/app/src/dispatcher/user.tsx

@@ -1,47 +0,0 @@
-/**
- * Copyright (c) Facebook, Inc. and its affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- *
- * @format
- */
-
-import {Store} from '../reducers/index';
-import {Logger} from '../fb-interfaces/Logger';
-import {login, logout} from '../reducers/user';
-import {getUser, logoutUser} from '../fb-stubs/user';
-import {sideEffect} from '../utils/sideEffect';
-import config from '../fb-stubs/config';
-
-export default (store: Store, _logger: Logger) => {
-  if (!config.isFBBuild) {
-    return;
-  }
-
-  getUser()
-    .then((user) => {
-      if (user) {
-        store.dispatch(login(user));
-      } else {
-        store.dispatch(logout());
-      }
-    })
-    .catch((e) => {
-      store.dispatch(logout());
-      console.warn('Failed to load user:', e);
-    });
-
-  let prevUserName = store.getState().user.name;
-  sideEffect(
-    store,
-    {name: 'logout', throttleMs: 500},
-    (state) => state.user.name,
-    (userName) => {
-      if (prevUserName && !userName) {
-        logoutUser();
-      }
-      prevUserName = userName;
-    },
-  );
-};