You need to annotate your Customer class with @Named or @Model annotation:
package de.java2enterprise.onlineshop.model;
@Model
public class Customer {
private String email;
private String password;
}
or create/modify beans.xml:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/beans_1_1.xsd"
bean-discovery-mode="all">
</beans>