[modbus_controller] Allow duplicate command config (#7311)

esphome/components/modbus_controller/modbus_controller.h

@@ -448,6 +448,12 @@ class ModbusController : public PollingComponent, public modbus::ModbusDevice {
   /// incoming queue
   void on_write_register_response(ModbusRegisterType register_type, uint16_t start_address,
                                   const std::vector<uint8_t> &data);
+  /// Allow a duplicate command to be sent
+  void set_allow_duplicate_commands(bool allow_duplicate_commands) {
+    this->allow_duplicate_commands_ = allow_duplicate_commands;
+  }
+  /// get if a duplicate command can be sent
+  bool get_allow_duplicate_commands() { return this->allow_duplicate_commands_; }
   /// called by esphome generated code to set the command_throttle period
   void set_command_throttle(uint16_t command_throttle) { this->command_throttle_ = command_throttle; }
   /// called by esphome generated code to set the offline_skip_updates
@@ -482,6 +488,8 @@ class ModbusController : public PollingComponent, public modbus::ModbusDevice {
   std::list<std::unique_ptr<ModbusCommandItem>> command_queue_;
   /// modbus response data waiting to get processed
   std::queue<std::unique_ptr<ModbusCommandItem>> incoming_queue_;
+  /// if duplicate commands can be sent
+  bool allow_duplicate_commands_;
   /// when was the last send operation
   uint32_t last_command_timestamp_;
   /// min time in ms between sending modbus commands