Added validation checks for employee creation

<SRS> SRS02 : Employee Management </SRS>

<Changes>
 - Added helper function to check for existing active employee of a given type
 - Enforced business rule to allow only one active employee per non-general type
 - Added duplicate email validation before employee creation
 - Added duplicate phone number validation before employee creation
</Changes>

<Review>
Smitha Mohan
</Review>

Trenser.Zenvy/Trenser.Zenvy/services/EmployeeManagementService.cpp

@@ -13,8 +13,48 @@
 #include "FileManager.h"
 #include "ApplicationConfig.h"
 
+static bool hasActiveEmployeeOfType(Enums::EmployeeType employeeType, const employeeMap& employees)
+{
+	for (const auto& employeePair : employees)
+	{
+		const auto& employee = employeePair.second;
+		if (employee->getEmployeeType() == employeeType && employee->getEmployeeAccountStatus() == Enums::AccountStatus::ACTIVE)
+		{
+			return true;
+		}
+	}
+	return false;
+}
+
+static bool isEmailDuplicate(const std::string& email, const employeeMap& employees)
+{
+	for (const auto& employeePair : employees)
+	{
+		const auto& employee = employeePair.second;
+		if (employee->getEmployeeEmail() == email)
+		{
+			return true;
+		}
+	}
+	return false;
+}
+
+static bool isPhoneDuplicate(const std::string& phone, const employeeMap& employees)
+{
+	for (const auto& employeePair : employees)
+	{
+		const auto& employee = employeePair.second;
+		if (employee->getEmployeePhone() == phone)
+		{
+			return true;
+		}
+	}
+	return false;
+}
+
 void EmployeeManagementService::createEmployee(Enums::EmployeeType employeeType, Enums::EmployeeDesignation employeeDesignation, const std::string& email, const std::string& name, const std::string& phone)
 {
+	auto& employees = m_dataStore.getEmployees();
 	std::shared_ptr<Employee> authenticatedEmployee = m_dataStore.getAuthenticatedEmployee();
 	if (!authenticatedEmployee)
 	{
@@ -23,6 +63,10 @@ void EmployeeManagementService::createEmployee(Enums::EmployeeType employeeType,
 	Enums::EmployeeType authenticatedEmployeeType = authenticatedEmployee->getEmployeeType();
 	std::shared_ptr<Employee> employee;
 	std::shared_ptr<Payroll> payroll;
+	if (employeeType != Enums::EmployeeType::GENERAL && hasActiveEmployeeOfType(employeeType, employees))
+	{
+		throw std::runtime_error("Cannot create more than one employee of type " + Enums::getEmployeeTypeString(employeeType));
+	}
 	if (!util::isEmailValid(email))
 	{
 		throw std::runtime_error("Invalid Email");
@@ -31,6 +75,14 @@ void EmployeeManagementService::createEmployee(Enums::EmployeeType employeeType,
 	{
 		throw std::runtime_error("Invalid Phone");
 	}
+	if (isEmailDuplicate(email, employees))
+	{
+		throw std::runtime_error("Duplicate Email");
+	}
+	if (isPhoneDuplicate(phone, employees))
+	{
+		throw std::runtime_error("Duplicate Phone Number!");
+	}
 	switch (employeeType)
 	{
 	case Enums::EmployeeType::HR:
@@ -42,7 +94,6 @@ void EmployeeManagementService::createEmployee(Enums::EmployeeType employeeType,
 			Config::Payroll::HR_MANAGER_EMPLOYER_PF_CONTRIBUTION);
 		employee = Factory::getObject<HRManager>(name, phone, email, payroll);
 		break;
-
 	case Enums::EmployeeType::IT:
 	case Enums::EmployeeType::FINANCE:
 	case Enums::EmployeeType::TEAM: