Add explanatory comment about why we changed Observer.tee to use unsafe subscribe

core/src/main/kotlin/net/corda/core/internal/InternalUtils.kt

@@ -192,6 +192,9 @@ fun <T> Observable<T>.bufferUntilSubscribed(): Observable<T> {
 @DeleteForDJVM
 fun <T> Observer<T>.tee(vararg teeTo: Observer<T>): Observer<T> {
     val subject = PublishSubject.create<T>()
+    // use unsafe subscribe, so that the teed subscribers will not get wrapped with SafeSubscribers,
+    // therefore a potential raw exception (non Rx) coming from a child -unsafe subscribed- observer
+    // will not unsubscribe all of the subscribers under the PublishSubject.
     subject.unsafeSubscribe(Subscribers.from(this))
     teeTo.forEach { subject.unsafeSubscribe(Subscribers.from(it)) }
     return subject