Add mobile app development documentation to clarify module usage

[Copilot]

Overview

This PR addresses issue #[issue_number] where users were confused about which module to use for mobile application development on WeChat Open Platform.

Problem

Users developing mobile applications (iOS/Android apps) that need to integrate WeChat features (login, sharing, payment) were unclear about:

• Which WxJava module to use for mobile app development
• Whether there's a dedicated module for mobile applications
• How the weixin-java-open module relates to mobile app integration

The confusion stemmed from the fact that "微信开放平台" (WeChat Open Platform) is where mobile applications are registered, but the weixin-java-open module's primary purpose wasn't clearly documented.

Solution

Added comprehensive documentation to clarify the module usage and mobile app integration approach:

Main README.md

• Added a 注意 (Notice) section after the module list explaining:
  • For mobile app WeChat Login: use weixin-java-open module for server-side OAuth authorization
  • For mobile app WeChat Pay: use weixin-java-pay module
  • Client-side integration requires official WeChat mobile SDK (iOS/Android)
  • Clarified that weixin-java-open is primarily for third-party platforms managing multiple Official Accounts/Mini Programs

weixin-java-open/README.md

• Added module description section explaining the primary use cases
• Added dedicated "移动应用开发说明" (Mobile Application Development Guide) section with:
  • Clear instructions for WeChat Login integration
  • WeChat Pay integration guidance (with reference to APP payment type)
  • WeChat Share requirements
  • Links to official WeChat documentation

Key Points

1. WxJava is a server-side SDK - mobile apps need both:

   • Server-side: WxJava modules (weixin-java-open for OAuth, weixin-java-pay for payments)
   • Client-side: Official WeChat mobile SDK for iOS/Android

2. No separate mobile module needed - mobile app developers should use existing modules:

   • weixin-java-open for WeChat Login OAuth on backend
   • weixin-java-pay for payment processing on backend

3. Clear documentation helps users understand the architecture and choose the right modules

Testing

• ✅ Build successful: mvn clean compile -DskipTests=true
• ✅ Code quality check passed: mvn checkstyle:check
• ✅ No code changes, only documentation improvements

This is a documentation-only change with no impact on existing functionality.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>开放平台移动应用开发是选择哪个模块呢？</issue_title>
<issue_description>我目前需要接入移动应用的，然后看到这么项目好像没有针对移动应用独立一个模块。请教一下用哪个就可以了</issue_description>

Comments on the Issue (you are @copilot in this section)

@binarywang 建议你阅读下wiki里的文档

Fixes #3729

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.