public StoreTestModel() {
    }

    public StoreTestModel(Integer id, String fieldOne, String fieldTwo) {
        this.id = id;
        this.fieldOne = fieldOne;
        this.fieldTwo = fieldTwo;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(updatable = false, nullable = false)
    private Integer id;

    @Column(name = "field_one")
    private String fieldOne;

    @Column(name = "field_two")
    private String fieldTwo;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getFieldOne() {
        return fieldOne;
    }

    public void setFieldOne(String fieldOne) {
        this.fieldOne = fieldOne;
    }

    public String getFieldTwo() {
        return fieldTwo;
    }

    public void setFieldTwo(String fieldTwo) {
        this.fieldTwo = fieldTwo;
    }
}

<persistence version="2.0"
             xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="
        http://java.sun.com/xml/ns/persistence
        http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
    <persistence-unit name="api-extensions">
        <jta-data-source>java:jboss/datasources/KeycloakDS</jta-data-source>

        <class>keycloak.apiextension.entity.StoreTestModel</class>

        <properties>
            <property name="hibernate.hbm2ddl.auto" value="none" />
            <property name="hibernate.show_sql" value="false" />
        </properties>
    </persistence-unit>
</persistence>

ERROR [org.keycloak.services.error.KeycloakErrorHandler] (default task-611) Uncaught server error: org.keycloak.models.ModelException: java.lang.IllegalArgumentException: org.hibernate.hql.internal.ast.QuerySyntaxException: store_test_model is not mapped [SELECT u FROM store_test_model u WHERE u.fieldOne = :fieldOne]