[PM-17563] [PM-19754] Migrate Security Task Module to libs/common (#14036)

* [PM-17563] Remove references to Angular from TaskService

* [PM-17563] Move Task module to libs/common/vault to avoid Angular dependency

* [PM-17563] Fix bad imports

* [PM-17563] Fix a few more missed imports

libs/common/src/vault/utils/observable-utilities.ts

@@ -0,0 +1,37 @@
+import { filter, Observable, OperatorFunction, shareReplay } from "rxjs";
+
+import { UserId } from "@bitwarden/common/types/guid";
+
+/**
+ * Builds an observable once per userId and caches it for future requests.
+ * The built observables are shared among subscribers with a replay buffer size of 1.
+ * @param create - A function that creates an observable for a given userId.
+ */
+export function perUserCache$<TValue>(
+  create: (userId: UserId) => Observable<TValue>,
+): (userId: UserId) => Observable<TValue> {
+  const cache = new Map<UserId, Observable<TValue>>();
+  return (userId: UserId) => {
+    let observable = cache.get(userId);
+    if (!observable) {
+      observable = create(userId).pipe(shareReplay({ bufferSize: 1, refCount: false }));
+      cache.set(userId, observable);
+    }
+    return observable;
+  };
+}
+
+/**
+ * Strongly typed observable operator that filters out null/undefined values and adjusts the return type to
+ * be non-nullable.
+ *
+ * @example
+ * ```ts
+ * const source$ = of(1, null, 2, undefined, 3);
+ * source$.pipe(filterOutNullish()).subscribe(console.log);
+ * // Output: 1, 2, 3
+ * ```
+ */
+export function filterOutNullish<T>(): OperatorFunction<T | undefined | null, T> {
+  return filter((v): v is T => v != null);
+}