Fixed UnrecognizedPropertyException.

```
Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "database" (class com.example.helloworld.HelloWorldConfiguration), not marked as ignorable (5 known properties: , "server", "template", "databaseConfiguration", "defaultName", "logging"])
 at [Source: N/A; line: -1, column: -1] (through reference chain: com.example.helloworld.HelloWorldConfiguration["database"])
```