Add directory interactions to the tech demo page

• Enter an SDMF directory read cap to see its children
• Click on its directory children to see their children
• Use standard forward/backward navigation to traverse interaction history

obelisk/common/src/Common/Route.hs

@@ -36,8 +36,10 @@ data FrontendRoute :: * -> * where
 
   -- | A technology demo page.  This is not part of the user-facing
   -- application proper.  Instead, it's a dumping ground for experiments and
-  -- demos.
-  FrontendRoute_TechDemo :: FrontendRoute ()
+  -- demos.  The payload is [] for the basic page and each time the directory
+  -- widget is used to navigate deeper into a directory hierarchy the visited
+  -- directory is pushed on the front of the list.
+  FrontendRoute_TechDemo :: FrontendRoute [Text]
 
   -- | Show the list of magic-folders
   FrontendRoute_MagicFolders :: FrontendRoute ()
@@ -63,7 +65,7 @@ fullRouteEncoder = mkFullRouteEncoder
       BackendRoute_Missing -> PathSegment "missing" $ unitEncoder mempty)
   (\case
       FrontendRoute_Main -> PathEnd $ unitEncoder mempty
-      FrontendRoute_TechDemo -> PathSegment "techdemo" $ unitEncoder mempty
+      FrontendRoute_TechDemo -> PathSegment "techdemo" $ pathOnlyEncoder
       FrontendRoute_MagicFolders -> PathSegment "magic-folders" $ unitEncoder mempty
       FrontendRoute_FileBrowser -> PathSegment "browse" $ pathOnlyEncoder
       FrontendRoute_AcceptFolderInvite -> PathSegment "folder-invite" $ pathOnlyEncoder . singletonListEncoder