fix(oauth): persist inviter for OAuth registrations

[zhangzhichaolove]

⚠️ 提交说明 / PR Notice

Important

• 请提供人工撰写的简洁摘要，避免直接粘贴未经整理的 AI 输出。
• 当前 git 用户不是仓库历史核心提交者之一。本次变更由 AI 辅助生成，提交前请人工复核。

📝 变更描述 / Description

OAuth 注册新用户时，后端已经从 session 中解析邀请人的 aff 并得到 inviterId，但事务插入路径 InsertWithTx 没有把该值保存到用户的 inviter_id 字段，导致 OAuth 注册用户缺少邀请归属。

本次修改让 InsertWithTx 在创建用户前写入 user.InviterId = inviterId，使 OAuth 注册与普通密码注册保持一致。同时新增模型层回归测试，覆盖有邀请人和无邀请人两种 OAuth 用户创建场景。

🚀 变更类型 / Type of change

• 🐛 Bug 修复 (Bug fix) - 请关联对应 Issue，避免将设计取舍、理解偏差或预期不一致直接归类为 bug
• ✨ 新功能 (New feature) - 重大特性建议先通过 Issue 沟通
• ⚡ 性能优化 / 重构 (Refactor)
• 📝 文档更新 (Documentation)

🔗 关联任务 / Related Issue

• Closes GitHub OAuth 注册时邀请人无法获得额度 #2774

✅ 提交前检查项 / Checklist

• 人工确认: 我已亲自整理并撰写此描述，没有直接粘贴未经处理的 AI 输出。
• 非重复提交: 我已搜索现有的 Issues 与 PRs，确认不是重复提交。
• Bug fix 说明: 若此 PR 标记为 Bug fix，我已提交或关联对应 Issue，且不会将设计取舍、预期不一致或理解偏差直接归类为 bug。
• 变更理解: 我已理解这些更改的工作原理及可能影响。
• 范围聚焦: 本 PR 未包含任何与当前任务无关的代码改动。
• 本地验证: 已在本地运行并通过测试或手动验证，维护者可以据此复核结果。
• 安全合规: 代码中无敏感凭据，且符合项目代码规范。

📸 运行证明 / Proof of Work

本地验证通过：

go test ./model

结果：

ok  	github.com/QuantumNous/new-api/model	1.451s

Summary by CodeRabbit

• Bug Fixes
  • Fixed OAuth user creation so inviter information is now saved correctly when accounts are created within an existing transaction.
  • Improved coverage with automated tests that confirm the stored inviter value is correct for both cases: with an inviter and without an inviter.

[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: 2fa4eb08-0bde-4a77-a553-513af84cc58e

📥 Commits

Reviewing files that changed from the base of the PR and between a5ab0f8 and 95f7e64.

📒 Files selected for processing (1)

• model/user.go

🚧 Files skipped from review as they are similar to previous changes (1)

• model/user.go

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Walkthrough

The transactional OAuth user insert now assigns inviterId before persisting the user. A new test inserts users with and without an inviter and verifies the stored inviter_id value.

Changes

OAuth inviter persistence

Layer / File(s)	Summary
Persist inviter id in InsertWithTx model/user.go, model/user_oauth_test.go	InsertWithTx now copies inviterId onto the User before tx.Create, and a transactional test verifies the stored inviter_id for cases with and without an inviter.

Estimated code review effort: 2 (Simple) | ~10 minutes

Poem

🐇 A hop, a tx, a tiny cue,
The inviter id now travels through.
Insert, then read, the trail stays clear,
The bunny says: “it’s stored right here!”

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: persisting inviter data during OAuth registrations.
Linked Issues check	✅ Passed	The code now stores inviterId in InsertWithTx and adds regression tests, matching the reported OAuth inviter-loss issue.
Out of Scope Changes check	✅ Passed	The changes are narrowly scoped to the OAuth inviter fix and its regression tests.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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