feat: runtime provider hotswap

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/location/provider.ts

@@ -7,6 +7,7 @@ import { SourceDisabledError } from "../sources/errors.ts"
 import { sources } from "../sources/user-sources.ts"
 
 export class LocationSourceProvider implements FeedSourceProvider {
+	readonly sourceId = "aelis.location"
 	private readonly db: Database
 
 	constructor(db: Database) {