Rework to only replace first instance of path

Author: alukach

src/stac_auth_proxy/middleware/ProcessLinksMiddleware.py

@@ -53,11 +53,12 @@ def transform_json(self, data: dict[str, Any], request: Request) -> dict[str, An
                     continue
 
                 # Remove the upstream_url path from the link if it exists
-                if urlparse(self.upstream_url).path != "/":
+                parsed_upstream_url = urlparse(self.upstream_url)
+                if parsed_upstream_url.path != "/" and parsed_link.path.startswith(
+                    parsed_upstream_url.path
+                ):
                     parsed_link = parsed_link._replace(
-                        path=str(parsed_link.path).replace(
-                            str(urlparse(self.upstream_url).path), ""
-                        )
+                        path=parsed_link.path[len(parsed_upstream_url.path) :]
                     )
 
                 # Add the root_path to the link if it exists