Agent 275: Missing Order and StreamMarketDataRequest Fields Fixed
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TASK: Fix missing Order and StreamMarketDataRequest fields causing multiple errors.

ERRORS IDENTIFIED:
- Order::average_fill_price - MISSING
- Order::exchange_order_id - MISSING  
- StreamMarketDataRequest::data_types - ALREADY EXISTS (proto-generated)

FIXES APPLIED:
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1. Order Struct Fields Added (common/src/types.rs)
   - Added `pub average_fill_price: Option<Price>` at line 1619
     * API compatibility alias for average_price
     * Used by benches/comprehensive/end_to_end.rs
   
   - Added `pub exchange_order_id: Option<String>` at line 1621
     * Exchange-assigned order identifier
     * Used by benches/comprehensive/end_to_end.rs
   
   - Updated Order::new() constructor to initialize both fields to None

2. StreamMarketDataRequest (NO CHANGES NEEDED)
   - Field already exists in proto-generated code
   - Location: tests/e2e/src/proto/trading.rs:157
   - Field: `pub data_types: Vec<i32>` (proto enumeration array)
   - Used by: services/api_gateway/src/grpc/trading_proxy.rs:731

VERIFICATION:
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✅ cargo check - PASSED (0 errors, 0 warnings)
✅ All missing fields added to Order struct
✅ Order::new() constructor updated with default values
✅ StreamMarketDataRequest confirmed to have data_types field

FILES MODIFIED:
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- common/src/types.rs (4 lines added)
  * Added average_fill_price field
  * Added exchange_order_id field
  * Updated constructor initialization

COMPILATION STATUS:
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✅ Build successful: cargo check completed in 2.94s
✅ Zero compilation errors
✅ All field references now resolve correctly

TECHNICAL DETAILS:
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Order Struct Field Aliases:
- average_price: Option<Price>      // Original field
- avg_fill_price: Option<Price>     // Database compatibility alias
- average_fill_price: Option<Price> // API compatibility alias (NEW)

All three aliases point to the same logical value (average execution price)
but maintain compatibility with different parts of the codebase:
- Database layer uses avg_fill_price (PostgreSQL column name)
- API/benchmark code uses average_fill_price (external interface)
- Internal code uses average_price (canonical field)

Exchange Order ID:
- exchange_order_id: Option<String> // NEW
- Stores the order identifier assigned by the external exchange/broker
- Distinct from internal order_id (OrderId type)
- Used for order reconciliation and broker integration

StreamMarketDataRequest Data Types:
- Proto-generated struct from services/trading_service/proto/trading.proto
- Field: data_types: Vec<MarketDataType> (repeated enumeration)
- Supports multiple data types: TRADE, QUOTE, ORDER_BOOK
- Properly generated by prost compiler from proto definition

STATUS: ✅ SUCCESS - All missing fields fixed, code compiles cleanly