Store the peer's MOQT implementation string.

Bug discovered in interop testing.

PiperOrigin-RevId: 826624979

quiche/quic/moqt/moqt_parser.cc

diff --git a/quiche/quic/moqt/moqt_parser.cc b/quiche/quic/moqt/moqt_parser.cc
index 3c1fc9f..2ef6958 100644
--- a/quiche/quic/moqt/moqt_parser.cc
+++ b/quiche/quic/moqt/moqt_parser.cc
@@ -1104,6 +1104,7 @@
 
 bool MoqtControlParser::KeyValuePairListToMoqtSessionParameters(
     const KeyValuePairList& parameters, MoqtSessionParameters& out) {
+  out.moqt_implementation = "";
   return parameters.ForEach(
       [&](uint64_t key, uint64_t value) {
         SetupParameter parameter = static_cast<SetupParameter>(key);
@@ -1147,6 +1148,7 @@
             break;
           case SetupParameter::kMoqtImplementation:
             QUICHE_LOG(INFO) << "Peer MOQT implementation: " << value;
+            out.moqt_implementation = value;
             break;
           default:
             break;