📦 refactor: Consolidate DB models, encapsulating Mongoose usage in data-schemas (#11830)

* chore: move database model methods to /packages/data-schemas

* chore: add TypeScript ESLint rule to warn on unused variables

* refactor: model imports to streamline access

- Consolidated model imports across various files to improve code organization and reduce redundancy.
- Updated imports for models such as Assistant, Message, Conversation, and others to a unified import path.
- Adjusted middleware and service files to reflect the new import structure, ensuring functionality remains intact.
- Enhanced test files to align with the new import paths, maintaining test coverage and integrity.

* chore: migrate database models to packages/data-schemas and refactor all direct Mongoose Model usage outside of data-schemas

* test: update agent model mocks in unit tests

- Added `getAgent` mock to `client.test.js` to enhance test coverage for agent-related functionality.
- Removed redundant `getAgent` and `getAgents` mocks from `openai.spec.js` and `responses.unit.spec.js` to streamline test setup and reduce duplication.
- Ensured consistency in agent mock implementations across test files.

* fix: update types in data-schemas

* refactor: enhance type definitions in transaction and spending methods

- Updated type definitions in `checkBalance.ts` to use specific request and response types.
- Refined `spendTokens.ts` to utilize a new `SpendTxData` interface for better clarity and type safety.
- Improved transaction handling in `transaction.ts` by introducing `TransactionResult` and `TxData` interfaces, ensuring consistent data structures across methods.
- Adjusted unit tests in `transaction.spec.ts` to accommodate new type definitions and enhance robustness.

* refactor: streamline model imports and enhance code organization

- Consolidated model imports across various controllers and services to a unified import path, improving code clarity and reducing redundancy.
- Updated multiple files to reflect the new import structure, ensuring all functionalities remain intact.
- Enhanced overall code organization by removing duplicate import statements and optimizing the usage of model methods.

* feat: implement loadAddedAgent and refactor agent loading logic

- Introduced `loadAddedAgent` function to handle loading agents from added conversations, supporting multi-convo parallel execution.
- Created a new `load.ts` file to encapsulate agent loading functionalities, including `loadEphemeralAgent` and `loadAgent`.
- Updated the `index.ts` file to export the new `load` module instead of the deprecated `loadAgent`.
- Enhanced type definitions and improved error handling in the agent loading process.
- Adjusted unit tests to reflect changes in the agent loading structure and ensure comprehensive coverage.

* refactor: enhance balance handling with new update interface

- Introduced `IBalanceUpdate` interface to streamline balance update operations across the codebase.
- Updated `upsertBalanceFields` method signatures in `balance.ts`, `transaction.ts`, and related tests to utilize the new interface for improved type safety.
- Adjusted type imports in `balance.spec.ts` to include `IBalanceUpdate`, ensuring consistency in balance management functionalities.
- Enhanced overall code clarity and maintainability by refining type definitions related to balance operations.

* feat: add unit tests for loadAgent functionality and enhance agent loading logic

- Introduced comprehensive unit tests for the `loadAgent` function, covering various scenarios including null and empty agent IDs, loading of ephemeral agents, and permission checks.
- Enhanced the `initializeClient` function by moving `getConvoFiles` to the correct position in the database method exports, ensuring proper functionality.
- Improved test coverage for agent loading, including handling of non-existent agents and user permissions.

* chore: reorder memory method exports for consistency

- Moved `deleteAllUserMemories` to the correct position in the exported memory methods, ensuring a consistent and logical order of method exports in `memory.ts`.

packages/api/src/middleware/balance.ts

@@ -1,13 +1,20 @@
 import { logger } from '@librechat/data-schemas';
+import type {
+  IBalanceUpdate,
+  BalanceConfig,
+  AppConfig,
+  ObjectId,
+  IBalance,
+  IUser,
+} from '@librechat/data-schemas';
 import type { NextFunction, Request as ServerRequest, Response as ServerResponse } from 'express';
-import type { IBalance, IUser, BalanceConfig, ObjectId, AppConfig } from '@librechat/data-schemas';
-import type { Model } from 'mongoose';
 import type { BalanceUpdateFields } from '~/types';
 import { getBalanceConfig } from '~/app/config';
 
 export interface BalanceMiddlewareOptions {
   getAppConfig: (options?: { role?: string; refresh?: boolean }) => Promise<AppConfig>;
-  Balance: Model<IBalance>;
+  findBalanceByUser: (userId: string) => Promise<IBalance | null>;
+  upsertBalanceFields: (userId: string, fields: IBalanceUpdate) => Promise<IBalance | null>;
 }
 
 /**
@@ -75,7 +82,8 @@ function buildUpdateFields(
  */
 export function createSetBalanceConfig({
   getAppConfig,
-  Balance,
+  findBalanceByUser,
+  upsertBalanceFields,
 }: BalanceMiddlewareOptions): (
   req: ServerRequest,
   res: ServerResponse,
@@ -97,18 +105,14 @@ export function createSetBalanceConfig({
         return next();
       }
       const userId = typeof user._id === 'string' ? user._id : user._id.toString();
-      const userBalanceRecord = await Balance.findOne({ user: userId }).lean();
+      const userBalanceRecord = await findBalanceByUser(userId);
       const updateFields = buildUpdateFields(balanceConfig, userBalanceRecord, userId);
 
       if (Object.keys(updateFields).length === 0) {
         return next();
       }
 
-      await Balance.findOneAndUpdate(
-        { user: userId },
-        { $set: updateFields },
-        { upsert: true, new: true },
-      );
+      await upsertBalanceFields(userId, updateFields);
 
       next();
     } catch (error) {