add system ID to ETA object in graphql schema

schema.graphqls

@@ -50,6 +50,7 @@ type ETA {
   shuttle: Shuttle
   shuttleId: ID!
   secondsRemaining: Float!
+  systemId: ID!
 }
 
 type Shuttle {

src/resolvers/ShuttleResolvers.ts

@@ -17,6 +17,7 @@ export const ShuttleResolvers: Resolvers<ServerContext> = {
         secondsRemaining: etaForStopId.secondsRemaining,
         shuttleId: parent.id,
         shuttle: parent,
+        systemId: system.id,
       };
     },
     etas: async (parent, args, contextValue, info) => {
@@ -35,6 +36,7 @@ export const ShuttleResolvers: Resolvers<ServerContext> = {
           stopId,
           shuttle: parent,
           shuttleId: parent.id,
+          systemId: system.id,
         }
       }));
 
@@ -56,7 +58,7 @@ export const ShuttleResolvers: Resolvers<ServerContext> = {
         id: route.id,
         name: route.name,
         polylineCoordinates: route.polylineCoordinates,
-        systemId: parent.systemId,
+        systemId: system.id,
       }
     }
   },