Add system ID prefix to all Redis keys to prevent cross-system ID clashes

When multiple university systems share the same Redis instance, entity IDs
(shuttles, stops, routes, etc.) could collide. This namespaces all Redis
keys with the system ID (e.g., `1:shuttle:stop:123` instead of
`shuttle:stop:123`).

- Add systemId field and prefixKey() helper to BaseRedisRepository
- Update all Redis repository subclasses to use prefixed keys
- Wire system ID from InterchangeSystem.build() into Redis repositories
- Add migration utility (migrateRedisKeysToSystemPrefix) with tests
- Update all test holders to pass a test system ID

https://claude.ai/code/session_012Vfz1NHWJbVtoDEWcE5tq6

src/repositories/shuttle/eta/BaseRedisETARepository.ts

@@ -3,11 +3,11 @@ import { BaseRedisRepository } from "../../BaseRedisRepository";
 import { ETAGetterRepository, ETARepositoryEvent, ETARepositoryEventListener, ETARepositoryEventName } from "./ETAGetterRepository";
 
 export abstract class BaseRedisETARepository extends BaseRedisRepository implements ETAGetterRepository {
-  private static readonly ETA_KEY_PREFIX = 'shuttle:eta:';
+  private get etaKeyPrefix() { return this.prefixKey('shuttle:eta:'); }
 
   // Helper methods
   protected createEtaKey = (shuttleId: string, stopId: string) =>
-    `${BaseRedisETARepository.ETA_KEY_PREFIX}${shuttleId}:${stopId}`;
+    `${this.etaKeyPrefix}${shuttleId}:${stopId}`;
 
   createRedisHashFromEta = (eta: IEta): Record<string, string> => ({
     secondsRemaining: eta.secondsRemaining.toString(),
@@ -27,7 +27,7 @@ export abstract class BaseRedisETARepository extends BaseRedisRepository impleme
 
   // Getter implementations
   async getEtasForShuttleId(shuttleId: string): Promise<IEta[]> {
-    const keys = await this.redisClient.keys(`${BaseRedisETARepository.ETA_KEY_PREFIX}${shuttleId}:*`);
+    const keys = await this.redisClient.keys(`${this.etaKeyPrefix}${shuttleId}:*`);
     const etas: IEta[] = [];
 
     for (const key of keys) {
@@ -41,7 +41,7 @@ export abstract class BaseRedisETARepository extends BaseRedisRepository impleme
   }
 
   async getEtasForStopId(stopId: string): Promise<IEta[]> {
-    const keys = await this.redisClient.keys(`${BaseRedisETARepository.ETA_KEY_PREFIX}*`);
+    const keys = await this.redisClient.keys(`${this.etaKeyPrefix}*`);
     const etas: IEta[] = [];
 
     for (const key of keys) {

src/repositories/shuttle/eta/RedisExternalSourceETARepository.ts

@@ -2,8 +2,17 @@ import { IEta } from "../../../entities/ShuttleRepositoryEntities";
 import { BaseRedisETARepository } from "./BaseRedisETARepository";
 import { ExternalSourceETARepository } from "./ExternalSourceETARepository";
 import { ETARepositoryEvent } from "./ETAGetterRepository";
+import { RedisClientType } from "redis";
+import createRedisClientForRepository from "../../../helpers/createRedisClientForRepository";
 
 export class RedisExternalSourceETARepository extends BaseRedisETARepository implements ExternalSourceETARepository {
+  constructor(
+    redisClient: RedisClientType = createRedisClientForRepository(),
+    systemId: string = '',
+  ) {
+    super(redisClient, systemId);
+  }
+
   async addOrUpdateEtaFromExternalSource(eta: IEta): Promise<void> {
     await this.addOrUpdateEta(eta);
   }

src/repositories/shuttle/eta/RedisSelfUpdatingETARepository.ts

@@ -13,8 +13,9 @@ export class RedisSelfUpdatingETARepository extends BaseRedisETARepository imple
     readonly shuttleRepository: ShuttleGetterRepository,
     redisClient: RedisClientType = createRedisClientForRepository(),
     private referenceTime: Date | null = null,
+    systemId: string = '',
   ) {
-    super(redisClient);
+    super(redisClient, systemId);
 
     this.setReferenceTime = this.setReferenceTime.bind(this);
     this.getAverageTravelTimeSeconds = this.getAverageTravelTimeSeconds.bind(this);
@@ -28,7 +29,7 @@ export class RedisSelfUpdatingETARepository extends BaseRedisETARepository imple
   }
 
   private createHistoricalEtaTimeSeriesKey = (routeId: string, fromStopId: string, toStopId: string) => {
-    return `shuttle:eta:historical:${routeId}:${fromStopId}:${toStopId}`;
+    return this.prefixKey(`shuttle:eta:historical:${routeId}:${fromStopId}:${toStopId}`);
   }
 
   setReferenceTime(referenceTime: Date) {

src/repositories/shuttle/eta/__tests__/ExternalSourceETARepositorySharedTests.test.ts

@@ -16,7 +16,7 @@ class RedisExternalSourceETARepositoryHolder implements RepositoryHolder<Externa
       url: process.env.REDIS_URL,
     });
     await this.redisClient.connect();
-    this.repo = new RedisExternalSourceETARepository(this.redisClient);
+    this.repo = new RedisExternalSourceETARepository(this.redisClient, 'test-system');
     return this.repo;
   }
   teardown = async () => {

src/repositories/shuttle/eta/__tests__/SelfUpdatingETARepositorySharedTests.test.ts

@@ -22,10 +22,12 @@ class RedisSelfUpdatingETARepositoryHolder implements RepositoryHolder<SelfUpdat
     });
     await this.redisClient.connect();
     await this.redisClient.flushAll();
-    this.shuttleRepo = new RedisShuttleRepository(this.redisClient);
+    this.shuttleRepo = new RedisShuttleRepository(this.redisClient, 0.001, 'test-system');
     this.repo = new RedisSelfUpdatingETARepository(
       this.shuttleRepo,
       this.redisClient,
+      null,
+      'test-system',
     );
     return this.repo;
   }