Use date only for days endpoint model

src/Electricity.Api/Models/Day.cs

@@ -2,19 +2,19 @@ using Electricity.Api.Extensions;
 
 namespace Electricity.Api.Models;
 
-public record Day(uint DateTime, double TotalPowerUse, double TotalPowerReturn, double TotalGasUse)
+public record Day(string Date, double TotalPowerUse, double TotalPowerReturn, double TotalGasUse)
 {
     public static Day Empty(DateOnly date)
     {
         return new Day(
-            date.ToDateTime(new TimeOnly(0, 0), DateTimeKind.Utc).ToEpoch(),
+            date.ToString(Constants.isoDateFormat),
             0, 0, 0);
     }
 
     public static Day FromEntity(Entities.ElectricityLog entity)
     {
         return new Day(
-            DateTime: entity.GetDateTime().ToEpoch(),
+            Date: entity.Date,
             TotalPowerUse: entity.TotalPowerConsumptionDay + entity.TotalPowerConsumptionNight,
             TotalPowerReturn: entity.TotalPowerReturnDay + entity.TotalPowerReturnNight,
             TotalGasUse: entity.GasConsumptionInCubicMeters

src/Electricity.Api/Services/ElectricityService.cs

@@ -56,9 +56,8 @@ public class ElectricityService
         }
 
         var lastAsModel = Day.FromEntity(last);
-        // TODO fix UTC issues here (just return the date, don't use timestamps)
         return new Day(
-            lastAsModel.DateTime,
+            lastAsModel.Date,
             lastAsModel.TotalPowerUse - firstAsModel.TotalPowerUse,
             lastAsModel.TotalPowerReturn - firstAsModel.TotalPowerReturn,
             lastAsModel.TotalGasUse - firstAsModel.TotalGasUse