chore: Update deleteUser method to handle non-existent users earlier

UserManagement/src/test/java/com/joe/trading/user_management/services/UserServiceImplTest.java

@@ -145,6 +145,7 @@ void updateUser_shouldThrowResourceNotFoundException_whenUserDoesNotExist() {
  @Test
  void deleteUser_shouldDeleteUser_whenNoPortfoliosExist() throws ResourceNotFoundException {
  when(portfolioRepository.findByUserId(1L)).thenReturn(Collections.emptyList());
+ when(userRepository.findById(1L)).thenReturn(Optional.of(user));
 
  userService.deleteUser(1L);
 
@@ -171,6 +172,7 @@ void deleteUser_shouldMarkUserAsPendingDelete_whenPortfoliosExist() throws Excep
  void deleteUser_shouldThrowUserDeletionException_whenNatsServiceFails() throws Exception {
  Portfolio portfolio = new Portfolio();
  when(portfolioRepository.findByUserId(1L)).thenReturn(Collections.singletonList(portfolio));
+ when(userRepository.findById(1L)).thenReturn(Optional.of(user));
  doThrow(new JsonProcessingException("Error") {
  }).when(natsService).publish(any(Event.class), any());