Add DDL auto configuration for SystemDB database

Author: ThuF

docs-help/docs/setup/setup-environment-variables.md

@@ -188,6 +188,7 @@ Parameter     | Description
 **DIRIGIBLE_DATABASE_DATASOURCE_NAME_SYSTEM**   | The name of the system data source used in this instance                                                 | _`SystemDB`_
 **DIRIGIBLE_DATABASE_TRANSFER_BATCH_SIZE**    | The batch size used during the data transfer                                                             | _`1000`_
 **DIRIGIBLE_DATABASE_SYSTEM_DIALECT** | The driver dialect for the SystemDB database _(e.g. `org.hibernate.dialect.PostgreSQLDialect`)_ | _`-`_
+**DIRIGIBLE_DATABASE_SYSTEM_DDL_AUTO** | The DDL auto configuration for the SystemDB database _(e.g. `update`, `create`, `create-drop`, `validate`, `none`)_ | _`-`_
 **DIRIGIBLE_DATABASE_SYSTEM_DRIVER**	| The driver used for the SystemDB database connection                                                     | _`org.h2.Driver`_
 **DIRIGIBLE_DATABASE_SYSTEM_URL**	| The JDBC url used for the SystemDB database connection                                                   | _`jdbc:h2:file:./target/dirigible/h2/SystemDB`_
 **DIRIGIBLE_DATABASE_SYSTEM_USERNAME**	| The username used for the SystemDB database connection                                                   | _`sa`_