Appender: add support for appending Long, Integer, Short and Boolean

[maartenbosteels]

Currently the DuckDBAppender supports appending objects of type java.lang.String and primitive types like int, short, boolean and long.

When appending to a table that has nullable columns, it would be very convenient to have methods for these wrapper classes:

• java.lang.Boolean
• java.lang.Long
• java.lang.Integer
• java.lang.Short

Given a class like

    class Person {
        Integer age;
        Long ssn;
    }

Currently, one has to write

    public void append(DuckDBAppender appender, Person person) throws SQLException {         
        appender.beginRow();
        if (person.age != null) {
            appender.append(person.age);
        } else {
            appender.append((String) null);
        }
        if (person.ssn != null) {
            appender.append(person.ssn);
        } else {
            appender.append((String) null);
        }
        appender.endRow();
    }

While it could become:

    public void append(DuckDBAppender appender, Person person) throws SQLException {
        appender.beginRow();
        appender.append(person.age);
        appender.append(person.ssn);
        appender.endRow();
    }

if DuckDBAppender would have support for the wrapper classes and do the null checking.

[maartenbosteels]

#140