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/Flex.js

@@ -0,0 +1,45 @@
+// @flow
+import * as React from "react";
+import styled from "styled-components";
+
+type JustifyValues =
+  | "center"
+  | "space-around"
+  | "space-between"
+  | "flex-start"
+  | "flex-end";
+
+type AlignValues =
+  | "stretch"
+  | "center"
+  | "baseline"
+  | "flex-start"
+  | "flex-end";
+
+type Props = {
+  column?: ?boolean,
+  shrink?: ?boolean,
+  align?: AlignValues,
+  justify?: JustifyValues,
+  auto?: ?boolean,
+  className?: string,
+  children?: React.Node,
+};
+
+const Flex = (props: Props) => {
+  const { children, ...restProps } = props;
+  return <Container {...restProps}>{children}</Container>;
+};
+
+const Container = styled.div`
+  display: flex;
+  flex: ${({ auto }) => (auto ? "1 1 auto" : "initial")};
+  flex-direction: ${({ column }) => (column ? "column" : "row")};
+  align-items: ${({ align }) => align};
+  justify-content: ${({ justify }) => justify};
+  flex-shrink: ${({ shrink }) => (shrink ? 1 : "initial")};
+  min-height: 0;
+  min-width: 0;
+`;
+
+export default Flex;