code: public static @Nonnull User getOrCreateByIdOrFullName(@Nonnull String idOrFullName) {
          return get(idOrFullName, true, Collections.emptyMap());
      }
docs: Get the user by ID or Full Name.
  <p>
  If the user does not exist, creates a new one on-demand.
  
  <p>
  Use {@link #getById} when you know you have an ID.
  In this method Jenkins will try to resolve the {@link User} by full name with help of various
  {@link hudson.tasks.UserNameResolver}.
  This is slow (see JENKINS-23281).
  
  @param idOrFullName User ID or full name
  @return User instance. It will be created on-demand.
  @since 2.91