default <I extends HasDbmsId> BUILDER withUsername(I id, String username) {
        return withUsername(id.getDbmsId(), username);
    }
Configures a username for the identified dbms. The username will then be
applied after the configuration has been read and after the System
properties have been applied.
<p>
This will not be saved in any configuration files!

@param <I> identification type
@param id the identification of the dbms
@param username to use for the identified dbms
@return this instance
runtime-parent/runtime-core/src/main/java/com/speedment/runtime/core/ApplicationBuilder.java