feat: 添加 Google OAuth 登录支持

[Laurc2004]

• 新增 Google OAuth 提供者实现，包括令牌交换和用户信息获取
• 在用户模型中添加 GoogleId 字段及相关查询方法
• 添加系统设置页面用于配置 Google OAuth 客户端信息
• 在前端登录和注册页面添加 Google 登录按钮
• 在用户状态更新时同步 GoogleId 字段

Summary by CodeRabbit

• New Features
  • Google OAuth sign-in: Users can now log in using their Google accounts
  • Google OAuth registration: New users can register via Google
  • Google account binding: Existing users can link their Google accounts
  • Configuration panel: Administrators can manage Google OAuth settings including API credentials in system settings

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: b0ec8fdd-9a51-4d12-9488-2cf774b661e6

📥 Commits

Reviewing files that changed from the base of the PR and between 960bf9c and ca49b3f.

📒 Files selected for processing (10)

• controller/misc.go
• controller/oauth.go
• controller/option.go
• model/user.go
• oauth/google.go
• setting/system_setting/google.go
• web/src/components/auth/LoginForm.jsx
• web/src/components/auth/RegisterForm.jsx
• web/src/components/settings/SystemSetting.jsx
• web/src/helpers/api.js

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Walkthrough

This pull request implements Google OAuth provider support end-to-end: adds Google provider ID and settings to backend models and configuration, creates a Google OAuth provider with token exchange and user info flows, updates controllers to expose Google OAuth status and handle provider bindings, and adds login/registration/configuration UI components on the frontend.

Changes

Cohort / File(s)	Summary
Model & Settings model/user.go, setting/system_setting/google.go	Extended User model with GoogleId field and methods (FillUserByGoogleId, IsGoogleIdAlreadyTaken); added GoogleSettings struct with client credentials and enabled flag.
OAuth Provider Implementation oauth/google.go	Implemented GoogleProvider with token exchange (via Google token endpoint), user info retrieval, and provider-specific bindings (IsUserIDTaken, FillUserByProviderID, SetProviderUserID).
Backend Controllers controller/misc.go, controller/oauth.go, controller/option.go	Updated GetStatus to return google_oauth and google_client_id; added google_id to OAuth user binding updates; added validation for google.enabled option checks.
Frontend Auth Components web/src/components/auth/LoginForm.jsx, web/src/components/auth/RegisterForm.jsx	Added Google login/register buttons with onClick handlers, loading states, and conditional rendering based on google_oauth status flag.
Frontend Settings & Helpers web/src/components/settings/SystemSetting.jsx, web/src/helpers/api.js	Added Google OAuth configuration card for client credentials and enabled toggle; implemented onGoogleOAuthClicked OAuth flow handler.

Sequence Diagram

sequenceDiagram
    participant User as User (Browser)
    participant Frontend as Frontend (LoginForm)
    participant Google as Google OAuth
    participant Backend as Backend (Controller)
    participant DB as Database

    User->>Frontend: Click "Login with Google"
    Frontend->>Frontend: handleGoogleClick: prepare state
    Frontend->>Google: Redirect to authorization endpoint<br/>(with client_id, redirect_uri, scope)
    Google->>User: Show consent screen
    User->>Google: Authorize
    Google->>Frontend: Redirect with authorization code
    Frontend->>Backend: POST /oauth/google/exchange<br/>(code from redirect)
    Backend->>Google: POST token endpoint<br/>(code + client credentials)
    Google->>Backend: Return access token
    Backend->>Google: GET userinfo endpoint<br/>(with access token)
    Google->>Backend: Return user profile (sub, email, name)
    Backend->>DB: Query/create user with GoogleId
    DB->>Backend: Return user
    Backend->>User: Login session established
    Frontend->>User: Redirect to dashboard

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• Feat: user agreement and privacy policy settings #1981: Both PRs extend the GetStatus response in controller/misc.go to include new status flags.
• feat: 关联 discord 账号 #1706: Both PRs implement a new OAuth provider following the same pattern (settings, model fields, controller updates, frontend integration).
• fix: redirect OAuth login in current page #3329: Both PRs modify the OAuth flow helpers in web/src/helpers/api.js, with this PR adding onGoogleOAuthClicked.

Suggested reviewers

• seefs001

Poem

🐰 Hops with glee,
Google logins now flow free,
OAuth's dance complete,
Frontend and backend meet! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 8.33% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat: 添加 Google OAuth 登录支持' clearly and specifically describes the main change: adding Google OAuth login support, which is the core objective of this pull request across all modified files.

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[seefs001]

现有自定义oauth登录已经可以完成google登录流程，不考虑增加