Switch popup redirect from 302 to script.

The client needs to receive the URL fragment from OIDC,
but Safari does not preserve it on 302 redirects:
https://bugs.webkit.org/show_bug.cgi?id=158420

lib/api/authn/webid-oidc.js

@@ -90,14 +90,12 @@ function middleware (oidc) {
 
   // Static assets related to authentication
   const authAssets = [
+    ['/.well-known/solid/login/', '../static/popup-redirect.html', false],
     ['/common/', 'solid-auth-client/dist-popup/popup.html'],
     ['/common/js/', 'solid-auth-client/dist-lib/solid-auth-client.bundle.js'],
     ['/common/js/', 'solid-auth-client/dist-lib/solid-auth-client.bundle.js.map']
   ]
-  authAssets.map(([path, file]) => routeResolvedFile(router, path, file))
-  // Redirect for .well-known login popup location
-  router.get('/.well-known/solid/login',
-    (req, res) => res.redirect('/common/popup.html'))
+  authAssets.map(args => routeResolvedFile(router, ...args))
 
   // Initialize the OIDC Identity Provider routes/api
   // router.get('/.well-known/openid-configuration', discover.bind(provider))

lib/utils.js

@@ -234,8 +234,8 @@ function reqToPath (req) {
 /**
  * Adds a route that serves a static file from another Node module
  */
-function routeResolvedFile (router, path, file) {
-  const fullPath = path + file.match(/[^/]+$/)
+function routeResolvedFile (router, path, file, appendFileName = true) {
+  const fullPath = appendFileName ? path + file.match(/[^/]+$/) : path
   const fullFile = require.resolve(file)
   router.get(fullPath, (req, res) => res.sendFile(fullFile))
 }

static/popup-redirect.html

@@ -0,0 +1 @@
+<script>location.replace(`/common/popup.html${location.hash}`)</script>