fix error messages and comments

(error messages for the sysadmin should be sent to the logs,
 not to the user)

django/allgo/api/v1/views.py

@@ -96,6 +96,5 @@ def jobs(request):
 class APIDownloadView(JobAuthMixin, View):
 
     def get(self, request, *args, **kwargs):
-        log.debug("ADV !")
-        msg = "The file should be delivered by Nginx, so you should not be able to view this message !"
-        return JsonResponse({'error': msg}, status=404)
+        log.error("datastore requests must be served by nginx (bad config!)")
+        return JsonResponse({'error': 'Internal Server Error'}, status=500)

django/setup/files/etc/nginx/conf.d/allgo.conf.template

@@ -19,8 +19,8 @@ server
   # location are presented in their application/priority order
 
   location /api/
-  { # API should be accessible only with token
-    # it has to be CORS compliant.
+  { # The CORS config allows any origin. These endpoints MUST NOT use
+    # authentication by cookie.
     if ($request_method = 'OPTIONS')
     {
       add_header 'Access-Control-Allow-Origin' '*';