This PR implements the missing "运营工具-商家转账API" (Business Operations - Merchant Transfer API) referenced in WeChat Pay document 4012711988. The issue reported that this API was not available in WxJava despite being documented by WeChat Pay.

What's Added

New Service Interface

• BusinessOperationTransferService - Complete service interface for business operations transfer functionality
• BusinessOperationTransferServiceImpl - Full implementation with proper RSA encryption handling

API Endpoints Implemented

• POST /v3/fund-app/operation/mch-transfer/transfer-bills - Create operation transfer
• GET /v3/fund-app/operation/mch-transfer/transfer-bills/out-bill-no/{out_bill_no} - Query by merchant bill number
• GET /v3/fund-app/operation/mch-transfer/transfer-bills/transfer-bill-no/{transfer_bill_no} - Query by WeChat transfer bill number

Bean Classes

• BusinessOperationTransferRequest - Request parameters with automatic RSA encryption for user names
• BusinessOperationTransferResult - Transfer creation response
• BusinessOperationTransferQueryRequest - Query request parameters
• BusinessOperationTransferQueryResult - Query response with full transfer details

Constants & Configuration

• Added WxPayConstants.OperationSceneId with predefined operation scene IDs (2001, 2002, 2003)
• Extended existing UserRecvPerception constants for business operations context
• Integrated service into WxPayService and BaseWxPayServiceImpl

Documentation & Examples

• BusinessOperationTransferExample - Comprehensive usage examples showing all API operations
• BusinessOperationTransferServiceTest - Complete unit test coverage

Key Features

✅ Automatic RSA Encryption - User names are automatically encrypted using RSA with OAEP padding
✅ Operation Scene Support - Built-in support for business operation scenarios (cash marketing, commission, promotion)
✅ User Receipt Perception - Configurable user-facing transfer descriptions
✅ Error Handling - Proper exception handling with meaningful error messages
✅ WeChat Pay v3 Compliance - Follows all v3 API standards and conventions

Usage Example

// Get the service
BusinessOperationTransferService service = wxPayService.getBusinessOperationTransferService();
// Create transfer request
BusinessOperationTransferRequest request = BusinessOperationTransferRequest.newBuilder()
 .appid("your_app_id")
 .outBillNo("OT" + System.currentTimeMillis())
 .operationSceneId(WxPayConstants.OperationSceneId.OPERATION_CASH_MARKETING)
 .openid("user_openid")
 .transferAmount(100)
 .transferRemark("运营活动奖励")
 .userRecvPerception(WxPayConstants.UserRecvPerception.CASH_MARKETING.CASH)
 .build();
// Execute transfer
BusinessOperationTransferResult result = service.createOperationTransfer(request);
// Query transfer status
BusinessOperationTransferQueryResult queryResult = service.queryOperationTransferByOutBillNo(outBillNo);

This implementation provides merchants with the complete business operations transfer functionality that was missing from WxJava, enabling them to use WeChat Pay's operation tools for daily business activities.

Fixes #3507.

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.