feat: pass targetOrigin in handleAuth error responses

Add targetOrigin parameter to error responses in the handleAuth function
to ensure error messages are only sent to the originating domain.

Author: Mearman

src/index.js

@@ -117,6 +117,7 @@ const handleAuth = async (request, env) => {
         provider,
         error: 'OAuth app client ID or secret is not configured.',
         errorCode: 'MISCONFIGURED_CLIENT',
+        targetOrigin: referringOrigin || origin,
       });
     }
 
@@ -136,6 +137,7 @@ const handleAuth = async (request, env) => {
         provider,
         error: 'OAuth app client ID or secret is not configured.',
         errorCode: 'MISCONFIGURED_CLIENT',
+        targetOrigin: referringOrigin || origin,
       });
     }