misc: add count of visible blocks to login view context (#28370)

src/authentic2/views.py

@@ -365,6 +365,7 @@ def login(request, template_name='authentic2/login.html',
         'methods': rendered_forms,
         # new definition
         'blocks': collections.OrderedDict((block['id'], block) for block in blocks),
+        'visible_blocks_count': len([x for x in blocks if not x['is_hidden']]),
         redirect_field_name: redirect_to,
     })
     return render(request, template_name, context)