feat(backend): add dewPoint data

backend/src/main/java/org/mercury/backend/BackendApplication.java

@@ -25,12 +25,28 @@ public class BackendApplication {
     @PostMapping("/sensor")
     SensorData newEmployee(@RequestBody SensorData sensorData) {
         if (sensorData.timestamp() == null) {
-            sensorData = new SensorData(sensorData.temperature(), sensorData.humidity(), System.currentTimeMillis());
+            double dewPoint = Math.round(calculateDewPoint(sensorData.temperature(), sensorData.humidity()) * 10.0) / 10.0;
+            sensorData = new SensorData(sensorData.temperature(), sensorData.humidity(), dewPoint, System.currentTimeMillis());
         }
         this.sensorData = sensorData;
         return sensorData;
     }
 
+    public static double calculateDewPoint(double temperature, double humidity) {
+        // Constants for the Magnus formula
+        final double a = 17.27;
+        final double b = 237.7;
+
+        // Convert relative humidity to a decimal
+        double rh = humidity / 100.0;
+
+        // Calculate alpha
+        double alpha = (a * temperature) / (b + temperature) + Math.log(rh);
+
+        // Calculate dew point
+        return (b * alpha) / (a - alpha);
+    }
+
     @GetMapping("/sensor")
     SensorData getSensorData() {
         return sensorData;

backend/src/main/java/org/mercury/backend/SensorData.java

@@ -1,4 +1,4 @@
 package org.mercury.backend;
 
-public record SensorData(double temperature, double humidity, Long timestamp) {
+public record SensorData(double temperature, double humidity, double dewPoint, Long timestamp) {
 }