SAKAI_CONFIG_ITEM hibernate creation fails with utf8mb4 db

SAKAI_CONFIG_ITEM added in KNL-1063 is confusingly created twice, once by Hibernate:

kernel/api/src/main/java/org/sakaiproject/config/api/HibernateConfigItem.hbm.xml

and once with SQL ddl:

kernel/kernel-impl/src/main/sql/mysql/sakai_config_item.sql

On mysql databases with default character set utf8mb4, the Hibernate creations (which seems to run first) fails:

java.sql.SQLSyntaxErrorException: Row size too large. The maximum row size for the used table type, not counting BLOBs, is 65535. This includes storage overhead, check the manual. You have to change some columns to TEXT or BLOBs

The SQL attempted is:

create table SAKAI_CONFIG_ITEM
(ID bigint not null auto_increment,
NODE varchar(255),
NAME varchar(255) not null,
VALUE varchar(4000),
RAW_VALUE varchar(4000),
TYPE varchar(255) not null,
DEFAULT_VALUE varchar(4000),
DESCRIPTION varchar(4000),
SOURCE varchar(255),
DEFAULTED bit not null,
REGISTERED bit not null,
SECURED bit not null,
DYNAMIC bit not null,
CREATED datetime not null,
MODIFIED datetime not null,
POLL_ON datetime,
primary key (ID)) ENGINE=InnoDB;

To fix this, it looks like the hbm.xml should be adjusted, although it seems there are some complications around this which the DDL SQL was presumably intended to avoid. It's sufficient to reduce the length of 4000 for these 4 fields to something a little smaller, e.g. 3500.

Although in the Sakai 11 conversion script, these are defined as LONGTEXT.