feat: decouple account sync logic from UserStorageController (#5078)

## Explanation

This PR moves the logic related to account syncing from
`UserStorageController` to separated files in the `account-syncing`
folder.
It also improves test coverage related to account syncing to 100%.


## References

Related to #4923

- Extension draft PR:
MetaMask/metamask-extension#29316
  - CI & E2E Passes ✅ 
- I needed to add the new `isAccountSyncingInProgress` state key at
various places to make it pass CI (as expected)
  - Account syncing is enabled on extension
- Mobile draft PR:
MetaMask/metamask-mobile#12755
  - CI passes BUT ✅ ☝️  
- I needed to add the new isAccountSyncingInProgress state key at
various places to make it pass CI (as expected)
- UTs were broken. It seems to be linked to the latest version of
`NetworkController` and its `NetworkController:networkDidChange` event.
This latest version is requested by our controller as part of the
upcoming network syncing feature.
- This will require a separate PR that bumps `NetworkController` to
`v22.1.1` (or another incriminated dependency TBD)
- This has started to be addressed here:
MetaMask/metamask-mobile#12765
- This was fixed by this PR: #5116
  - In any case, account syncing is **NOT** enabled on mobile yet

## Changelog

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### `@metamask/profile-sync-controller`

- **CHANGED**: moved account syncing logic to its own files
- **BREAKING**: added a new `isAccountSyncingInProgress` state key

## Checklist

- [x] I've updated the test suite for new or updated code as appropriate
- [x] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [x] I've highlighted breaking changes using the "BREAKING" category
above as appropriate
- [x] I've prepared draft pull requests for clients and consumer
packages to resolve any breaking changes

packages/profile-sync-controller/src/controllers/user-storage/__fixtures__/test-utils.ts

@@ -1,3 +1,65 @@
+import type nock from 'nock';
+
+import encryption from '../../../shared/encryption/encryption';
+import type {
+  GetUserStorageAllFeatureEntriesResponse,
+  GetUserStorageResponse,
+} from '../services';
+import { MOCK_STORAGE_KEY } from './mockStorage';
+
+/**
+ * Test Utility - creates a realistic mock user-storage entry
+ * @param data - data to encrypt
+ * @returns user storage entry
+ */
+export async function createMockUserStorageEntry(
+  data: unknown,
+): Promise<GetUserStorageResponse> {
+  return {
+    HashedKey: 'HASHED_KEY',
+    Data: await encryption.encryptString(
+      JSON.stringify(data),
+      MOCK_STORAGE_KEY,
+    ),
+  };
+}
+
+/**
+ * Test Utility - creates a realistic mock user-storage get-all entry
+ * @param data - data array to encrypt
+ * @returns user storage entry
+ */
+export async function createMockUserStorageEntries(
+  data: unknown[],
+): Promise<GetUserStorageAllFeatureEntriesResponse> {
+  return await Promise.all(data.map((d) => createMockUserStorageEntry(d)));
+}
+
+/**
+ * Test Utility - decrypts a realistic batch upsert payload
+ * @param requestBody - nock body
+ * @param storageKey - storage key
+ * @returns decrypted body
+ */
+export async function decryptBatchUpsertBody(
+  requestBody: nock.Body,
+  storageKey: string,
+) {
+  if (typeof requestBody === 'string') {
+    return requestBody;
+  }
+  return await Promise.all(
+    Object.entries<string>(requestBody.data).map(
+      async ([entryKey, entryValue]) => {
+        return [
+          entryKey,
+          await encryption.decryptString(entryValue, storageKey),
+        ];
+      },
+    ),
+  );
+}
+
 type WaitForOptions = {
   intervalMs?: number;
   timeoutMs?: number;

packages/profile-sync-controller/src/controllers/user-storage/__fixtures__/mockAccounts.ts → packages/profile-sync-controller/src/controllers/user-storage/account-syncing/__fixtures__/mockAccounts.ts

@@ -2,8 +2,8 @@ import { EthAccountType } from '@metamask/keyring-api';
 import { KeyringTypes } from '@metamask/keyring-controller';
 import type { InternalAccount } from '@metamask/keyring-internal-api';
 
-import { LOCALIZED_DEFAULT_ACCOUNT_NAMES } from '../accounts/constants';
-import { mapInternalAccountToUserStorageAccount } from '../accounts/user-storage';
+import { LOCALIZED_DEFAULT_ACCOUNT_NAMES } from '../constants';
+import { mapInternalAccountToUserStorageAccount } from '../utils';
 
 /**
  * Map an array of internal accounts to an array of user storage accounts

packages/profile-sync-controller/src/controllers/user-storage/account-syncing/__fixtures__/test-utils.ts

@@ -0,0 +1,68 @@
+import type { InternalAccount } from '@metamask/keyring-internal-api';
+
+import { createSHA256Hash } from '../../../../shared/encryption';
+import { mockUserStorageMessenger } from '../../__fixtures__/mockMessenger';
+import { mapInternalAccountToUserStorageAccount } from '../utils';
+import { MOCK_INTERNAL_ACCOUNTS } from './mockAccounts';
+
+/**
+ * Test Utility - create a mock user storage messenger for account syncing tests
+ *
+ * @param options - options for the mock messenger
+ * @param options.accounts - options for the accounts part of the controller
+ * @param options.accounts.accountsList - list of accounts to return for the 'AccountsController:listAccounts' action
+ * @returns Mock User Storage Messenger
+ */
+export function mockUserStorageMessengerForAccountSyncing(options?: {
+  accounts?: {
+    accountsList?: InternalAccount[];
+  };
+}) {
+  const messengerMocks = mockUserStorageMessenger();
+
+  messengerMocks.mockKeyringAddNewAccount.mockImplementation(async () => {
+    messengerMocks.baseMessenger.publish(
+      'AccountsController:accountAdded',
+      MOCK_INTERNAL_ACCOUNTS.ONE[0] as InternalAccount,
+    );
+    return MOCK_INTERNAL_ACCOUNTS.ONE[0].address;
+  });
+
+  messengerMocks.mockAccountsListAccounts.mockReturnValue(
+    (options?.accounts?.accountsList ??
+      MOCK_INTERNAL_ACCOUNTS.ALL) as InternalAccount[],
+  );
+
+  return messengerMocks;
+}
+
+/**
+ * Test Utility - creates a realistic expected batch upsert payload
+ * @param data - data supposed to be upserted
+ * @param storageKey - storage key
+ * @returns expected body
+ */
+export function createExpectedAccountSyncBatchUpsertBody(
+  data: [string, InternalAccount][],
+  storageKey: string,
+) {
+  return data.map(([entryKey, entryValue]) => [
+    createSHA256Hash(String(entryKey) + storageKey),
+    JSON.stringify(mapInternalAccountToUserStorageAccount(entryValue)),
+  ]);
+}
+
+/**
+ * Test Utility - creates a realistic expected batch delete payload
+ * @param data - data supposed to be deleted
+ * @param storageKey - storage key
+ * @returns expected body
+ */
+export function createExpectedAccountSyncBatchDeleteBody(
+  data: string[],
+  storageKey: string,
+) {
+  return data.map((entryKey) =>
+    createSHA256Hash(String(entryKey) + storageKey),
+  );
+}