Expose numberOfTransfers in GTFS GraphQL API

src/main/java/org/opentripplanner/apis/gtfs/datafetchers/ItineraryImpl.java

@@ -71,6 +71,11 @@ public DataFetcher<Iterable<Leg>> legs() {
     return environment -> getSource(environment).getLegs();
   }
 
+  @Override
+  public DataFetcher<Integer> numberOfTransfers() {
+    return environment -> getSource(environment).getNumberOfTransfers();
+  }
+
   @Override
   public DataFetcher<Long> startTime() {
     return environment -> getSource(environment).startTime().toInstant().toEpochMilli();

src/main/java/org/opentripplanner/apis/gtfs/generated/GraphQLDataFetchers.java

@@ -409,6 +409,8 @@ public interface GraphQLItinerary {
 
     public DataFetcher<Iterable<Leg>> legs();
 
+    public DataFetcher<Integer> numberOfTransfers();
+
     public DataFetcher<Long> startTime();
 
     public DataFetcher<Iterable<SystemNotice>> systemNotices();

src/main/resources/org/opentripplanner/apis/gtfs/schema.graphqls

@@ -1546,6 +1546,13 @@ type Itinerary {
     """
     accessibilityScore: Float
 
+    """
+    How many transfers are contained in this itinerary.
+
+    Note: Interlined/stay-seated transfers also increase the count.
+    """
+    numberOfTransfers: Int
+
     #
     # deprecated fields
     #

src/test/resources/org/opentripplanner/apis/gtfs/expectations/plan-extended.json

@@ -10,6 +10,7 @@
           "emissionsPerPerson" : {
             "co2" : 123.0
           },
+          "numberOfTransfers" : 1,
           "legs" : [
             {
               "mode" : "WALK",

src/test/resources/org/opentripplanner/apis/gtfs/queries/plan-extended.graphql

@@ -23,6 +23,7 @@
             emissionsPerPerson {
                 co2
             }
+            numberOfTransfers
             legs {
                 mode
                 from {