allow thekno apps to take part in origin trials

system-files/nginx-spa.conf

@@ -2,6 +2,10 @@ location / {
   # try to resolve files and always fallback to the index.html file
   try_files $uri $uri/ /index.html;
 
+  # if this domain participates in an origin trial we set the appropriate header
+  # see: https://googlechrome.github.io/OriginTrials/developer-guide.html
+  add_header Origin-Trial "$origin_trial";
+
   location ~* "\.(?:[0-9a-f]{8,32})\.(?:[0-9a-z]+)$" {
     # cache immutable files (indicated by the contained hash) indefinitely
     add_header Cache-Control "public, immutable, max-age=365000000";