[PM-6072] Add get$ method on SendService (#7839)

* Added missing get$ method on SendService

* Added distinctUntilChanged to the get$ method and added more tests

* Added more validations and tests to get$

* Added some more test cases to get$

* Refactored test cases from get$

libs/common/src/tools/send/services/send.service.abstraction.ts

@@ -18,7 +18,17 @@ export abstract class SendService {
     password: string,
     key?: SymmetricCryptoKey,
   ) => Promise<[Send, EncArrayBuffer]>;
+  /**
+   * @deprecated Do not call this, use the get$ method
+   */
   get: (id: string) => Send;
+  /**
+   * Provides a send for a determined id
+   * updates after a change occurs to the send that matches the id
+   * @param id The id of the desired send
+   * @returns An observable that listens to the value of the desired send
+   */
+  get$: (id: string) => Observable<Send | undefined>;
   /**
    * Provides re-encrypted user sends for the key rotation process
    * @param newUserKey The new user key to use for re-encryption