config/src/main/java/org/springframework/security/config/annotation/authentication/configurers/provisioning/UserDetailsManagerConfigurer.java
@SuppressWarnings("unchecked")
	public final UserDetailsBuilder withUser(String username) {
		UserDetailsBuilder userBuilder = new UserDetailsBuilder((C) this);
		userBuilder.username(username);
		this.userBuilders.add(userBuilder);
		return userBuilder;
	}
@SuppressWarnings("unchecked")
	public final UserDetailsBuilder withUser(String username) {
		UserDetailsBuilder userBuilder = new UserDetailsBuilder((C) this);
		userBuilder.username(username);
		this.userBuilders.add(userBuilder);
		return userBuilder;
	}
Allows adding a user to the {@link UserDetailsManager} that is being created. This
method can be invoked multiple times to add multiple users.

@param username the username for the user being added. Cannot be null.
@return the {@link UserDetailsBuilder} for further customizations