closes #12168 nginx reverse proxy opds (#12170)

* closes #12168 nginx reverse proxy opds
* fix opds, add cors
* Add CORS headers to /opds location

Author: mekarpeles

docker/web_nginx.conf

@@ -112,6 +112,35 @@ server {
       return 429 '{"status": 429, "message": "Too Many Requests. Consider using https://openlibrary.org/developers/dumps."}';
     }
 
+    location /opds/ {
+        proxy_pass https://ol-opds.prod.archive.org/;
+
+        add_header Access-Control-Allow-Origin "*" always;
+        add_header Access-Control-Allow-Methods "GET, POST, OPTIONS" always;
+        add_header Access-Control-Allow-Headers "Content-Type, Authorization" always;
+
+        # Handle preflight
+        if ($request_method = OPTIONS) {
+            return 204;
+        }
+
+        add_header X-OPDS-Backend "ol-opds.prod.archive.org" always;
+        proxy_ssl_server_name on;
+        proxy_set_header Host ol-opds.prod.archive.org;
+        proxy_set_header X-Forwarded-For $remote_addr;
+        proxy_set_header X-Forwarded-Proto $scheme;
+
+        # optional but usually needed
+        proxy_redirect off;
+    }
+
+    location = /opds {
+        add_header Access-Control-Allow-Origin "*" always;
+        add_header Access-Control-Allow-Methods "GET, OPTIONS" always;
+        add_header Access-Control-Allow-Headers "Content-Type" always;
+        return 308 /opds/;
+    }
+
     location / {
         limit_req zone=web_limit burst=100 delay=10;
         limit_req zone=ua_rate_limit burst=25 delay=10;