fix invalid headers when proxying HTTPS

etc/nginx/villas.conf

+# If we receive X-Forwarded-Proto, pass it through; otherwise, pass along the
+# scheme used to connect to this server
+map $http_x_forwarded_proto $proxy_x_forwarded_proto {
+  default $http_x_forwarded_proto;
+  ''      $scheme;
+}
+
+# If we receive X-Forwarded-Port, pass it through; otherwise, pass along the
+# server port the client connected to
+map $http_x_forwarded_port $proxy_x_forwarded_port {
+  default $http_x_forwarded_port;
+  ''      $server_port;
+}
+
+# If we receive Upgrade, set Connection to "upgrade"; otherwise, delete any
+# Connection header that may have been passed to this server
+map $http_upgrade $proxy_connection {
+  default upgrade;
+  '' close;
+}
+
+# Set appropriate X-Forwarded-Ssl header
+map $scheme $proxy_x_forwarded_ssl {
+  default off;
+  https on;
+}
+
+# HTTP 1.1 support
+proxy_http_version 1.1;
+proxy_buffering off;
+proxy_set_header Host $http_host;
+proxy_set_header Upgrade $http_upgrade;
+proxy_set_header Connection $proxy_connection;
+proxy_set_header X-Real-IP $remote_addr;
+proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+proxy_set_header X-Forwarded-Proto $proxy_x_forwarded_proto;
+proxy_set_header X-Forwarded-Ssl $proxy_x_forwarded_ssl;
+proxy_set_header X-Forwarded-Port $proxy_x_forwarded_port;
+
 server {
   listen      80 default_server;
   server_name VILLASweb;
@@ -24,9 +63,6 @@ server {
 
   location /ws {
     proxy_pass http://node/;
-    proxy_http_version 1.1;
-    proxy_set_header Upgrade $http_upgrade;
-    proxy_set_header Connection "upgrade";
   }
 
   # frontend location
@@ -41,8 +77,5 @@ server {
 
   location / {
     proxy_pass http://node/;
-    proxy_http_version 1.1;
-    proxy_set_header Upgrade $http_upgrade;
-    proxy_set_header Connection "upgrade";
   }
 }