introduce unified_session_id and extend performance stats with target bitrate (#1113)

Author: thesyncim

protobuf/video/sfu/models/models.pb.go

@@ -413,4 +413,6 @@ message PerformanceStats {
   float avg_fps = 4;
   // the track dimensions
   VideoDimension video_dimension = 5;
+  // the target bitrate for the track, only for published tracks
+  int32 target_bitrate = 6;
 }

protobuf/video/sfu/models/models.proto

@@ -87,6 +87,10 @@ message SendStatsRequest {
   repeated models.PerformanceStats encode_stats = 16;
   // Decode stats for the subscriber
   repeated models.PerformanceStats decode_stats = 17;
+  // user_session id can change during reconnects, this helps us to
+  // identify the user across reconnects and should remain consistent until the user explicitly
+  // disconnects, is kicked or the call is ended.
+  string unified_session_id = 18;
 }
 
 message SendStatsResponse {