feat: runtime provider hotswap (#82)

Add ability to replace a FeedSourceProvider at runtime and propagate
the new source to all active (and pending) user sessions, invalidating
their feed caches.

Co-authored-by: Ona <no-reply@ona.com>

apps/aelis-backend/src/tfl/provider.ts

@@ -16,6 +16,7 @@ const tflConfig = type({
 })
 
 export class TflSourceProvider implements FeedSourceProvider {
+	readonly sourceId = "aelis.tfl"
 	private readonly db: Database
 	private readonly apiKey: string | undefined
 	private readonly client: ITflApi | undefined