New login screen (#1331)

* wip

* feat: first draft of auth.config

* chore: auth methodS

* chore: styling

* styling, styling, styling

* feat: Auth notices

* chore: Remove server-rendered pages, move shared/components -> components

* lint

* cleanup

* cleanup

* fix: Remove unused component

* fix: Ensure env variables in prod too

* style tweaks

* fix: Entering SSO email into login form fails
fix: Tweak language around guest signin

app/components/Mask.js

@@ -3,7 +3,7 @@ import * as React from "react";
 import styled from "styled-components";
 import { pulsate } from "shared/styles/animations";
 import { randomInteger } from "shared/random";
-import Flex from "shared/components/Flex";
+import Flex from "components/Flex";
 
 type Props = {
   header?: boolean,