truncate long http debug messages (#21466)

Author: adameat

ydb/library/actors/http/http_proxy.cpp

@@ -445,6 +445,9 @@ TString GetObfuscatedData(TString data, const THeaders& headers) {
             data.replace(pos, x_yacloud_subjecttoken.size(), TString("<obfuscated>"));
         }
     }
+    if (data.size() > 1000) {
+        return data.substr(0, 500) + " --- <truncated> --- " + data.substr(data.size() - 500);
+    }
     return data;
 }