Reconfiguring the database configuration

Firstly, we will convert the current JBCP calendar project. Let's begin by reconfiguring the database.

We can begin by removing the DataSourceConfig.java file, as we will be leveraging Spring Boot's built-in support for an embedded H2 database. We will also need to remove the reference to DataSourceConfig.java in the JavaConfig.java file, as there is currently a reference to JavaConfig.java inside the @Import annotation.