fix: preserve capitalization in custom headers

Express converts all header names to lowercase, which prevents custom headers with uppercase characters from being properly passed to the target service. This fix ensures that custom headers preserve their original capitalization when forwarded through the proxy.

Author: Littly

server/src/index.ts

@@ -70,8 +70,9 @@ const getHttpHeaders = (
   // If the header "x-custom-auth-header" is present, use its value as the custom header name.
   if (req.headers["x-custom-auth-header"] !== undefined) {
     const customHeaderName = req.headers["x-custom-auth-header"] as string;
-    if (req.headers[customHeaderName] !== undefined) {
-      const value = req.headers[customHeaderName];
+    const lowerCaseHeaderName = customHeaderName.toLowerCase();
+    if (req.headers[lowerCaseHeaderName] !== undefined) {
+      const value = req.headers[lowerCaseHeaderName];
       headers[customHeaderName] = value as string;
     }
   }