* subscription loader now only pulls active subscriptions
only allow websocket connections to subscriptions of type websocket
* Added a "flag for deletion" to ActiveSubscription in the SubscriptionRegistry to handle the race condition of a scheduled sync overlapping with a subscription creation. We could have used a package-scoped semaphore or a pre-remove FHIR read, but this seemed like the safest, simplest and most performant way to handle it.
* ActiveSubscriptionCacheTest
* WebsocketConnectionValidatorTest
* fix compile error in jpa example