Resolves #186 Switch for group with same domain antities

lib/entity_class/group_entity.class.dart

@@ -0,0 +1,43 @@
+part of '../main.dart';
+
+class GroupEntity extends Entity {
+  GroupEntity(Map rawData) : super(rawData);
+
+  final List<String> _domainsForSwitchableGroup = ["switch", "light", "automation", "input_boolean"];
+  String mutualDomain;
+  bool switchable = false;
+
+  @override
+  Widget _buildStatePart(BuildContext context) {
+    if (switchable) {
+      return SwitchStateWidget(
+        domainForService: "homeassistant",
+      );
+    } else {
+      return super._buildStatePart(context);
+    }
+  }
+
+  @override
+  void update(Map rawData) {
+    super.update(rawData);
+    if (_isOneDomain()) {
+      mutualDomain = attributes['entity_id'][0].split(".")[0];
+      switchable = _domainsForSwitchableGroup.contains(mutualDomain);
+    }
+  }
+
+  bool _isOneDomain() {
+    bool result = false;
+    if (attributes['entity_id'] != null && attributes['entity_id'] is List && attributes['entity_id'].isNotEmpty) {
+      String firstChildDomain = attributes['entity_id'][0].split(".")[0];
+      result = true;
+      attributes['entity_id'].forEach((childEntityId){
+        if (childEntityId.split(".")[0] != firstChildDomain) {
+          result = false;
+        }
+      });
+    }
+    return result;
+  }
+}