add fields for cache and ttls

src/repositories/ApiBasedRepository.ts

@@ -14,6 +14,9 @@ export interface ApiBasedRepositoryCache {
   shuttleByShuttleId?: {
     [shuttleId: string]: IShuttle,
   },
+  shuttlesBySystemId?: {
+    [systemId: string]: IShuttle[],
+  },
   // To speed things up, implement caches for other data later
 }
 
@@ -21,6 +24,7 @@ export interface ApiBasedRepositoryMillisecondTTLs {
   etasForShuttleId?: number,
   etasForStopId?: number,
   shuttleByShuttleId?: number,
+  shuttlesBySystemId?: number,
 }
 
 const emptyCache: ApiBasedRepositoryCache = {