add support for SensorStateClass (used for long term statistics) and use it as default for Temperature and Humidity sensors

src/ha.h

@@ -289,6 +289,7 @@ namespace Ha {
     struct Sensor : Component, State {
         const char* unitMeasure = nullptr;
         unsigned int precision = 2;
+        const char* sensorStateClass = nullptr;
         inline static unordered_map<string, Sensor*> mapSensors;
 
         Sensor(const char* name, const char* id) : Component(id, name, "sensor"), State(this) {
@@ -301,6 +302,7 @@ namespace Ha {
             State::buildConfig(jsonDoc);
             if (unitMeasure) jsonDoc["unit_of_measurement"] = unitMeasure;
             if (isNumericSensor()) jsonDoc["suggested_display_precision"] = precision;
+            if (sensorStateClass) jsonDoc["state_class"] = sensorStateClass;
         }
 
     private:
@@ -313,6 +315,7 @@ namespace Ha {
         TemperatureSensor(const char* id, const char* name = "Temperature") : Sensor(name, id) {
             deviceClass = "temperature";
             unitMeasure = "°C";
+            sensorStateClass = "measurement";
         }
     };
 
@@ -320,6 +323,7 @@ namespace Ha {
         HumiditySensor(const char* id, const char* name = "Humidity") : Sensor(name, id) {
             deviceClass = "humidity";
             unitMeasure = "%";
+            sensorStateClass = "measurement";
         }
     };
 
@@ -407,6 +411,11 @@ namespace Ha {
             return *this;
         }
 
+        Builder& withSensorStateClass(const char* value) {
+            cmp->sensorStateClass = value;
+            return *this;
+        }
+
         Builder& withMin(unsigned int value) {
             cmp->min = value;
             return *this;