Refactor Google Sheets integration for better modularity and testability

- Decoupled Google Sheets API interaction into `GoogleSheetsClient`.
- Decoupled OAuth2 device code flow logic and state into `DeviceAuthProvider`.
- Refactored `sheets.service.ts` to use these new components while maintaining the existing public API.
- Added comprehensive unit tests for `GoogleSheetsClient` and `DeviceAuthProvider`.
- Improved type safety by using `OAuth2Client` instead of `any`.
- Ensured consistency with original behavior by including `responseRanges` in `batchUpdate`.

Co-authored-by: cpvalente <34649812+cpvalente@users.noreply.github.com>

apps/server/src/api-data/sheets/__tests__/GoogleSheetsClient.test.ts

@@ -0,0 +1,60 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { sheets } from '@googleapis/sheets';
+import { GoogleSheetsClient } from '../GoogleSheetsClient.js';
+
+vi.mock('@googleapis/sheets', () => ({
+  sheets: vi.fn(),
+}));
+
+describe('GoogleSheetsClient', () => {
+  let mockSheets: any;
+
+  beforeEach(() => {
+    mockSheets = {
+      spreadsheets: {
+        get: vi.fn(),
+        values: {
+          get: vi.fn(),
+        },
+        batchUpdate: vi.fn(),
+      },
+    };
+    (sheets as any).mockReturnValue(mockSheets);
+  });
+
+  it('should call spreadsheets.get', async () => {
+    const client = new GoogleSheetsClient({} as any);
+    mockSheets.spreadsheets.get.mockResolvedValue({ data: {} });
+    await client.getSpreadsheet('id');
+    expect(mockSheets.spreadsheets.get).toHaveBeenCalledWith({
+      spreadsheetId: 'id',
+      includeGridData: false,
+    });
+  });
+
+  it('should call spreadsheets.values.get', async () => {
+    const client = new GoogleSheetsClient({} as any);
+    mockSheets.spreadsheets.values.get.mockResolvedValue({ data: {} });
+    await client.getValues('id', 'range');
+    expect(mockSheets.spreadsheets.values.get).toHaveBeenCalledWith({
+      spreadsheetId: 'id',
+      valueRenderOption: 'FORMATTED_VALUE',
+      majorDimension: 'ROWS',
+      range: 'range',
+    });
+  });
+
+  it('should call spreadsheets.batchUpdate', async () => {
+    const client = new GoogleSheetsClient({} as any);
+    mockSheets.spreadsheets.batchUpdate.mockResolvedValue({ data: {} });
+    await client.batchUpdate('id', [{ updateCells: {} }], ['range']);
+    expect(mockSheets.spreadsheets.batchUpdate).toHaveBeenCalledWith({
+      spreadsheetId: 'id',
+      requestBody: {
+        includeSpreadsheetInResponse: false,
+        responseRanges: ['range'],
+        requests: [{ updateCells: {} }],
+      },
+    });
+  });
+});