Add history endpoint and do some cleanup

Environment/Service/Models/ReadingsGrouped.cs

@@ -0,0 +1,25 @@
+using JetBrains.Annotations;
+
+namespace ChrisKaczor.HomeMonitor.Environment.Service.Models;
+
+[PublicAPI]
+public class ReadingsGrouped
+{
+    public DateTimeOffset Bucket { get; set; }
+
+    public string? Name { get; set; }
+
+    public decimal AverageTemperature { get; set; }
+
+    public decimal AveragePressure { get; set; }
+
+    public decimal AverageHumidity { get; set; }
+
+    public decimal AverageLuminance { get; set; }
+
+    public decimal AverageGasResistance { get; set; }
+
+    public decimal AverageColorTemperature { get; set; }
+
+    public decimal AverageAirQualityIndex { get; set; }
+}