client/web: add advanced login options

This adds an expandable section of the login view to allow users to
specify an auth key and an alternate control URL.

Input and Collapsible components and accompanying styles were brought
over from the adminpanel.

Updates #10261

Signed-off-by: Will Norris <will@tailscale.com>

client/web/src/ui/collapsible.tsx

@@ -0,0 +1,33 @@
+import * as Primitive from "@radix-ui/react-collapsible"
+import React, { useState } from "react"
+import { ReactComponent as ChevronDown } from "src/assets/icons/chevron-down.svg"
+
+type CollapsibleProps = {
+  trigger?: string
+  children: React.ReactNode
+  open?: boolean
+  onOpenChange?: (open: boolean) => void
+}
+
+export default function Collapsible(props: CollapsibleProps) {
+  const { children, trigger, onOpenChange } = props
+  const [open, setOpen] = useState(props.open)
+
+  return (
+    <Primitive.Root
+      open={open}
+      onOpenChange={(open) => {
+        setOpen(open)
+        onOpenChange?.(open)
+      }}
+    >
+      <Primitive.Trigger className="inline-flex items-center text-gray-600 cursor-pointer hover:bg-stone-100 rounded text-sm font-medium pr-3 py-1 transition-colors">
+        <span className="ml-2 mr-1.5 group-hover:text-gray-500 -rotate-90 state-open:rotate-0">
+          <ChevronDown strokeWidth={3} className="stroke-gray-400 w-4" />
+        </span>
+        {trigger}
+      </Primitive.Trigger>
+      <Primitive.Content className="mt-2">{children}</Primitive.Content>
+    </Primitive.Root>
+  )
+}