Add UID2 (Unified ID 2.0) support in OpenRTB requests

- Check for UID2 tokens in cookies (__uid2_advertising_token or uid2)
- Add UID2 token to OpenRTB user.ext.eids array with proper source format
- Improve user identification capabilities with additional identifier
- Format UID2 according to OpenRTB specifications

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: bokelley

src/index.js

@@ -466,6 +466,12 @@ function buildOpenRtbRequest(url, etag, lastModified, request) {
     console.log(`[ID] Found LiveRamp envelope but source is not verified (_lr_env_src_ats = ${lrEnvSource}), skipping`);
   }
 
+  // Check for UID2 token (Unified ID 2.0)
+  const uid2Token = cookies['__uid2_advertising_token'] || cookies['uid2'] || null;
+  if (uid2Token) {
+    console.log(`[ID] Found UID2 token: ${uid2Token.substring(0, 10)}...`);
+  }
+  
   // Create OpenRTB request format
   const openRtbRequest = {
     site: {
@@ -523,6 +529,16 @@ function buildOpenRtbRequest(url, etag, lastModified, request) {
     });
   }
 
+  // Add UID2 token to eids if available
+  if (uid2Token) {
+    openRtbRequest.user.ext.eids.push({
+      source: "uidapi.com",
+      uids: [{
+        id: uid2Token
+      }]
+    });
+  }
+  
   // Only include user object if we have IDs
   if (openRtbRequest.user.ext.eids.length === 0) {
     delete openRtbRequest.user;