application.yml jpa: hibernate.ddl-auto: update code example

Example: spring.jpa.hibernate.ddl-auto

59.2 Initialize a database using Hibernate

You can set spring.jpa.hibernate.ddl-auto explicitly and the 
standard Hibernate property values are none, validate, update, create-drop. 
Spring Boot chooses a default value for you based on whether it thinks 
your database is embedded (default create-drop) or not (default none). 
An embedded database is detected by looking at the Connection type: hsqldb, 
h2 and derby are embedded, the rest are not. Be careful when switching from 
in-memory to a “real” database that you don’t make assumptions about the 
existence of the tables and data in the new platform. You either have to 
set ddl-auto explicitly, or use one of the other mechanisms to initialize 
the database.

In addition, a file named import.sql in the root of the classpath will be 
executed on startup. This can be useful for demos and for testing if you 
are careful, but probably not something you want to be on the classpath in 
production. It is a Hibernate feature (nothing to do with Spring).