@ConstructorBinding
@ConfigurationProperties("my.nested.config.props")
data class MyNestedConfigProps(
    val parentField1: String = "undefined",
    val parentField2: String = "undefined",
    val child: Child = Child(),
)

data class Child(
    val childField1: String = "undefined",
    val childField2: String = "undefined",
)

@SpringBootApplication
@EnableConfigurationProperties(MyNestedConfigProps::class)
class MainApp

fun main(args: Array<String>) {
    runApplication<MainApp>(*args)
}

my.nested.config.props.parent-filed-1=parent-field-1-value
my.nested.config.props.parent-filed-2=parent-field-2-value
my.nested.config.props.child.child-filed-1=child-field-1-value
my.nested.config.props.child.child-filed-2=child-field-2-value

my.nested.config.props:
  parent-field-1: parent-field-1-value
  parent-field-2: parent-field-2-value
  child:
    child-field-1: child-field-1-value
    child-field-2: child-field-2-value