Add admin token support to phosphor

This token will get special privileges in the proxies to bypass some security checks. Only select users will be able to get them

PiperOrigin-RevId: 705558102
diff --git a/quiche/blind_sign_auth/proto/public_metadata.proto b/quiche/blind_sign_auth/proto/public_metadata.proto
index 1e93e98..31b993b 100644
--- a/quiche/blind_sign_auth/proto/public_metadata.proto
+++ b/quiche/blind_sign_auth/proto/public_metadata.proto
@@ -49,6 +49,7 @@
   enum DebugMode {
     UNSPECIFIED_DEBUG_MODE = 0;
     DEBUG_ALL = 1;
+    ADMIN = 2;
   }
 
   DebugMode debug_mode = 4;