Add changePassword method in controller and authenticated user accessor

<UserStory> AUTH004 : Change Password </UserStory>

    <Changes>
    - Added changePassword method in ZenvyController to move to AuthenticationManagementService
    - Declared changePassword in ZenvyController.h
    - Introduced getAuthenticatedUser() in DataStore for accessing authenticated employee
    - Updated DataStore.h with getAuthenticatedUser() method
    - Prepared AuthenticationManagementService.cpp for password change implementation
    </Changes>

    <Review>
    Smitha Mohan
    </Review>

Trenser.Zenvy/Trenser.Zenvy/services/AuthenticationManagementService.h

@@ -2,6 +2,7 @@
 #include <string>
 #include <map>
 #include <utility>
+#include <stdexcept>
 #include "DataStore.h"
 #include "Enums.h"
 
@@ -13,6 +14,6 @@ public:
 	AuthenticationManagementService() : m_dataStore(DataStore::getInstance()) {};
 	std::tuple<Enums::LoginStatus, Enums::EmployeeType, Enums::EmployeeDesignation> login(const std::string& username, const std::string& password);
 	void logout();
-	void changePassword();
+	void changePassword(std::string);
 };