fix: Preserve HTTPS X-Forwarded-Proto in Nginx and configure SECURE_PROXY_SSL_HEADER in Django to fix 403 CSRF verification on Django Admin

frontend/nginx.conf

@@ -1,3 +1,8 @@
+map $http_x_forwarded_proto $forwarded_proto {
+    default $http_x_forwarded_proto;
+    ''      $scheme;
+}
+
 server {
     listen 80;
     server_name localhost;
@@ -29,25 +34,25 @@ server {
 
     location /api/ {
         proxy_pass http://backend:8000/api/;
-        proxy_set_header Host $host;
+        proxy_set_header Host $http_host;
         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 $scheme;
+        proxy_set_header X-Forwarded-Proto $forwarded_proto;
     }
 
     location /admin/ {
         proxy_pass http://backend:8000/admin/;
-        proxy_set_header Host $host;
+        proxy_set_header Host $http_host;
         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 $scheme;
+        proxy_set_header X-Forwarded-Proto $forwarded_proto;
     }
 
     location /static/ {
         proxy_pass http://backend:8000/static/;
-        proxy_set_header Host $host;
+        proxy_set_header Host $http_host;
         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 $scheme;
+        proxy_set_header X-Forwarded-Proto $forwarded_proto;
     }
 }