Add FlatPaymentController with RESTful payment endpoints

Introduced FlatPaymentController under Distribution.Features.Payment, providing GET and POST endpoints at /api/payments. Supports listing, retrieving, and creating payments with filtering and error handling. Business logic is delegated to PaymentService.

Distribution/Features/Grn/GrnController.cs

@@ -6,6 +6,16 @@ namespace Distribution.Features.Grn;
 [ApiController]
 public class GrnController(GrnService service, ICurrentUserService currentUser) : ControllerBase
 {
+    [HttpGet("api/goods-receipts")]
+    public async Task<IActionResult> GetAll(
+        [FromQuery] Guid? purchaseOrderId,
+        [FromQuery] int page = 1,
+        [FromQuery] int pageSize = 20)
+    {
+        var result = await service.GetAllAsync(purchaseOrderId, page, pageSize);
+        return Ok(result);
+    }
+
     [HttpGet("api/goods-receipts/{id:guid}")]
     public async Task<IActionResult> GetById(Guid id)
     {
@@ -13,6 +23,19 @@ public class GrnController(GrnService service, ICurrentUserService currentUser)
         return result is null ? NotFound() : Ok(result);
     }
 
+    [HttpPost("api/goods-receipts")]
+    public async Task<IActionResult> CreateFlat(CreateFlatGrnRequest request, CancellationToken ct)
+    {
+        var userId = currentUser.UserId ?? throw new UnauthorizedAccessException();
+        try
+        {
+            var inner = new CreateGrnRequest(request.WarehouseId, request.Items);
+            var result = await service.CreateAsync(request.PurchaseOrderId, inner, userId, ct);
+            return CreatedAtAction(nameof(GetById), new { id = result.Id }, result);
+        }
+        catch (InvalidOperationException ex) { return Conflict(new { error = ex.Message }); }
+    }
+
     [HttpGet("api/purchase-orders/{id:guid}/goods-receipts")]
     public async Task<IActionResult> GetByPurchaseOrder(Guid id) =>
         Ok(await service.GetByPurchaseOrderIdAsync(id));