[PM-15061] extract encryptors from generator service (#12068)

* introduce legacy encryptor provider
* port credential generation service to encryptor provider

libs/common/src/tools/cryptography/legacy-encryptor-provider.ts

@@ -0,0 +1,42 @@
+import { Observable } from "rxjs";
+
+import {
+  OrganizationBound,
+  SingleOrganizationDependency,
+  SingleUserDependency,
+  UserBound,
+} from "../dependencies";
+
+import { OrganizationEncryptor } from "./organization-encryptor.abstraction";
+import { UserEncryptor } from "./user-encryptor.abstraction";
+
+/** Creates encryptors
+ *  @deprecated this logic will soon be replaced with a design that provides for
+ *    key rotation. Use it at your own risk
+ */
+export abstract class LegacyEncryptorProvider {
+  /** Retrieves an encryptor populated with the user's most recent key instance that
+   *  uses a padded data packer to encode data.
+   *  @param frameSize length of the padded data packer's frames.
+   *  @param dependencies.singleUserId$ identifies the user to which the encryptor is bound
+   *  @returns an observable that emits when the key becomes available and completes
+   *    when the key becomes unavailable.
+   */
+  userEncryptor$: (
+    frameSize: number,
+    dependencies: SingleUserDependency,
+  ) => Observable<UserBound<"encryptor", UserEncryptor>>;
+
+  /** Retrieves an encryptor populated with the organization's most recent key instance that
+   *  uses a padded data packer to encode data.
+   *  @param frameSize length of the padded data packer's frames.
+   *  @param dependencies.singleOrganizationId$ identifies the user/org combination
+   *   to which the encryptor is bound.
+   *  @returns an observable that emits when the key becomes available and completes
+   *    when the key becomes unavailable.
+   */
+  organizationEncryptor$: (
+    frameSize: number,
+    dependences: SingleOrganizationDependency,
+  ) => Observable<OrganizationBound<"encryptor", OrganizationEncryptor>>;
+}