bq: fix string representation

pb.Tag_String_ is a byte array, so we need to convert it to String before saving it.

Change-Id: Ib336cfe16be0d9ca3390fc550a8d6efcd5f033b0

eventkitd-bigquery/bigquery/record.go

@@ -57,7 +57,7 @@ func (r *Record) Save() (map[string]bigquery.Value, string, error) {
 		case *pb.Tag_Int64:
 			fields[field] = v.Int64
 		case *pb.Tag_String_:
-			fields[field] = v.String_
+			fields[field] = string(v.String_)
 		case *pb.Tag_Timestamp:
 			fields[field] = time.Unix(v.Timestamp.Seconds, int64(v.Timestamp.Nanos))
 		}