Type as expected by the DBMS, e.g. VARCHAR or VARCHAR(254). Note that Slick's model omits
the optional length ascription for string columns here and carries the length in the
separate ColumnOption Length instead. A length ascription for string column is allowed
though and can be used in a Slick Table subclass to pass it to the DBMS. As this is the
type of the underlying DBMS it may not be portable to other DBMS.
Note that Slick uses VARCHAR or VARCHAR(254) in DDL for String columns if neither
ColumnOption DBType nor Length are given.