feat: Add support for named variables in IEnvironment

include/MantleAPI/Execution/i_environment.h

 /*******************************************************************************
  * Copyright (c) 2021-2023, Bayerische Motoren Werke Aktiengesellschaft (BMW AG)
+ * Copyright (c) 2024, Mercedes-Benz Tech Innovation GmbH
  *
  * This program and the accompanying materials are made
  * available under the terms of the Eclipse Public License 2.0
@@ -28,11 +29,17 @@
 #include <MantleAPI/Traffic/i_entity_repository.h>
 #include <MantleAPI/Traffic/i_traffic_swarm_service.h>
 
+#include <cstdint>
 #include <optional>
 #include <string>
+#include <variant>
 
 namespace mantle_api
 {
+
+/// @brief Allowed data types for parameters defined in a parameter declaration.
+using ParameterType = std::variant<bool, mantle_api::Time, double, std::string, std::uint32_t, std::uint16_t, std::int32_t>;
+
 /// Base interface for the environment conditions (e.g. time of day, weather, road condition) of a scenario
 class IEnvironment
 {
@@ -50,7 +57,7 @@ public:
   ///
   /// @param entity The entity to be manipulated by the specified controller.
   /// @param controller_id Identifies the controller to manipulate the entity.
-  virtual void AddEntityToController(IEntity& entity, UniqueId controller_id) = 0; // NOLINT (google-runtime-references)
+  virtual void AddEntityToController(IEntity& entity, UniqueId controller_id) = 0;  // NOLINT (google-runtime-references)
 
   /// Removes an entity from the specified controller.
   ///
@@ -157,6 +164,18 @@ public:
   /// @return The user defined value. No value if it doesn't exist.
   virtual std::optional<std::string> GetUserDefinedValue(const std::string& name) = 0;
 
+  /// @brief Sets a named variable
+  ///
+  /// @param name   The name of the variable
+  /// @param value  The value
+  virtual void SetVariable(const std::string& name, const ParameterType& value) = 0;
+
+  /// @brief Gets a named variable if it exists
+  ///
+  /// @param name  The name of the variable
+  /// @return The variable. No value if it doesn't exist.
+  [[nodiscard]] virtual std::optional<ParameterType> GetVariable(const std::string& name) const = 0;
+
   /// @brief Specifies how to behave if no route is available
   ///        or if an entity has reached the end of a route
   ///

test/MantleAPI/Test/test_utils.h

 /*******************************************************************************
  * Copyright (c) 2021-2024, Bayerische Motoren Werke Aktiengesellschaft (BMW AG)
  * Copyright (c) 2022 Ansys, Inc.
+ * Copyright (c) 2024, Mercedes-Benz Tech Innovation GmbH
  *
  * This program and the accompanying materials are made
  * available under the terms of the Eclipse Public License 2.0
@@ -573,7 +574,17 @@ public:
               (mantle_api::Time date_time),
               (override));
 
-  mantle_api::Time GetDateTime() override { return mantle_api::Time(); }
+  MOCK_METHOD(void,
+              SetVariable,
+              (const std::string& name, const ParameterType& value),
+              (override));
+
+  MOCK_METHOD(std::optional<ParameterType>,
+              GetVariable,
+              (const std::string& name),
+              (const, override));
+
+  mantle_api::Time GetDateTime() override { return {}; }
 
   MOCK_METHOD(mantle_api::Time, GetSimulationTime, (), (override));