Add asset information for Fan

This commit is to add asset information according to the Redfish Fan
schema.
If the `xyz.openbmc_project.Inventory.Decorator.Asset` interface does
not exist, the asset information property is not displayed.

ref: https://redfish.dmtf.org/schemas/v1/Fan.v1_3_0.json

Tested: Validator passes
'''
1. doGet method to get Fan asset information
curl -k https://${bmc}/redfish/v1/Chassis/chassis/ThermalSubsystem/Fans/fan0
{
  "@odata.id": "/redfish/v1/Chassis/chassis/ThermalSubsystem/Fans/fan0",
  "@odata.type": "#Fan.v1_3_0.Fan",
  "Id": "fan0",
  "Manufacturer": "Delta",
  "Model": "7B5F",
  "Name": "Fan",
  "PartNumber": "02YK323",
  "SerialNumber": "YL12JP1C1234",
  "SparePartNumber": "02YK323",
  "Status": {
    "Health": "OK",
    "State": "Enabled"
  }
}
'''

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I1840f2b372fea57ba6e5c499ba21c968f0005695
Signed-off-by: Lakshmi Yadlapati <lakshmiy@us.ibm.com>
diff --git a/redfish-core/lib/fan.hpp b/redfish-core/lib/fan.hpp
index fb2ba20..0acb762 100644
--- a/redfish-core/lib/fan.hpp
+++ b/redfish-core/lib/fan.hpp
@@ -278,6 +278,63 @@
         });
 }
 
+inline void getFanAsset(const std::shared_ptr<bmcweb::AsyncResp>& asyncResp,
+                        const std::string& fanPath, const std::string& service)
+{
+    sdbusplus::asio::getAllProperties(
+        *crow::connections::systemBus, service, fanPath,
+        "xyz.openbmc_project.Inventory.Decorator.Asset",
+        [fanPath, asyncResp{asyncResp}](
+            const boost::system::error_code& ec,
+            const dbus::utility::DBusPropertiesMap& assetList) {
+        if (ec)
+        {
+            if (ec.value() != EBADR)
+            {
+                BMCWEB_LOG_ERROR << "DBUS response error for Properties"
+                                 << ec.value();
+                messages::internalError(asyncResp->res);
+            }
+            return;
+        }
+        const std::string* manufacturer = nullptr;
+        const std::string* model = nullptr;
+        const std::string* partNumber = nullptr;
+        const std::string* serialNumber = nullptr;
+        const std::string* sparePartNumber = nullptr;
+
+        const bool success = sdbusplus::unpackPropertiesNoThrow(
+            dbus_utils::UnpackErrorPrinter(), assetList, "Manufacturer",
+            manufacturer, "Model", model, "PartNumber", partNumber,
+            "SerialNumber", serialNumber, "SparePartNumber", sparePartNumber);
+        if (!success)
+        {
+            messages::internalError(asyncResp->res);
+            return;
+        }
+        if (manufacturer != nullptr)
+        {
+            asyncResp->res.jsonValue["Manufacturer"] = *manufacturer;
+        }
+        if (model != nullptr)
+        {
+            asyncResp->res.jsonValue["Model"] = *model;
+        }
+        if (partNumber != nullptr)
+        {
+            asyncResp->res.jsonValue["PartNumber"] = *partNumber;
+        }
+        if (serialNumber != nullptr)
+        {
+            asyncResp->res.jsonValue["SerialNumber"] = *serialNumber;
+        }
+        if (sparePartNumber != nullptr && !sparePartNumber->empty())
+        {
+            asyncResp->res.jsonValue["SparePartNumber"] = *sparePartNumber;
+        }
+        });
+}
+
 inline void
     afterGetValidFanPath(const std::shared_ptr<bmcweb::AsyncResp>& asyncResp,
                          const std::string& chassisId, const std::string& fanId,
@@ -286,6 +343,7 @@
     addFanCommonProperties(asyncResp->res, chassisId, fanId);
     getFanState(asyncResp, fanPath, service);
     getFanHealth(asyncResp, fanPath, service);
+    getFanAsset(asyncResp, fanPath, service);
 }
 
 inline void doFanGet(const std::shared_ptr<bmcweb::AsyncResp>& asyncResp,