haproxy.cfg

+    acl acl:{{$endpoint}}:is_options method OPTIONS
+    use_backend cors_backend if acl:{{$endpoint}}:is_options


+backend cors_backend
+    errorfile 503 /etc/haproxy/options.http

options.http

+HTTP/1.1 200 OK
+Access-Control-Allow-Headers: Origin, Accept, X-Session_id, Content-Type
+Access-Control-Allow-Origin: *
+Access-Control-Allow-Credentials: true
+Access-Control-Max-Age: 86400
+Access-Control-Allow-Methods: HEAD, DELETE, POST, GET, OPTIONS, PUT
+Connection: close