Add option to share bookmarks publicly (#503)

* Make shared view public, add user profile fallback

* Allow unauthenticated access to shared bookmarks API

* Link shared bookmarks in unauthenticated layout

* Add public sharing setting

* Only show shared bookmarks link if there are publicly shared bookmarks

* Disable public sharing if sharing is disabled

* Show specific helper text when public sharing is enabled

* Fix tests

* Add more tests

* Improve setting description

siteroot/settings/base.py

@@ -52,6 +52,7 @@ MIDDLEWARE = [
     'django.middleware.common.CommonMiddleware',
     'django.middleware.csrf.CsrfViewMiddleware',
     'django.contrib.auth.middleware.AuthenticationMiddleware',
+    'bookmarks.middlewares.UserProfileMiddleware',
     'django.contrib.messages.middleware.MessageMiddleware',
     'django.middleware.clickjacking.XFrameOptionsMiddleware',
     'django.middleware.locale.LocaleMiddleware',
@@ -71,6 +72,7 @@ TEMPLATES = [
                 'django.contrib.auth.context_processors.auth',
                 'django.contrib.messages.context_processors.messages',
                 'bookmarks.context_processors.toasts',
+                'bookmarks.context_processors.public_shares',
             ],
         },
     },