Add mass to EntityProperties

MantleAPI/include/MantleAPI/Traffic/entity_properties.h

 /*******************************************************************************
- * Copyright (c) 2021, Bayerische Motoren Werke Aktiengesellschaft (BMW AG)
+ * Copyright (c) 2021-2022, Bayerische Motoren Werke Aktiengesellschaft (BMW AG)
  *
  * This program and the accompanying materials are made
  * available under the terms of the Eclipse Public License 2.0
@@ -47,6 +47,7 @@ struct EntityProperties
   EntityType type{EntityType::kOther};
   std::string model{};
   std::map<std::string, std::string> properties{};
+  units::mass::kilogram_t mass{};
 };
 
 inline bool operator==(const EntityProperties& lhs, const EntityProperties& rhs) noexcept