Use BeforeConvertCallback to generate entity identifiers.

Related ticket: spring-projects/spring-data-relational#1232
See #636

Author: mp911de

jdbc/howto/idgeneration/src/main/java/example.springdata/jdbc/howto/idgeneration/IdGenerationApplication.java

@@ -5,7 +5,7 @@
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.context.annotation.Bean;
-import org.springframework.data.relational.core.mapping.event.BeforeSaveCallback;
+import org.springframework.data.relational.core.mapping.event.BeforeConvertCallback;
 
 @SpringBootApplication
 class IdGenerationApplication {
@@ -15,9 +15,9 @@ public static void main(String[] args) {
 	}
 
 	@Bean
-	BeforeSaveCallback<StringIdMinion> beforeSaveCallback() {
+	BeforeConvertCallback<StringIdMinion> beforeSaveCallback() {
 
-		return (minion, mutableAggregateChange) -> {
+		return (minion) -> {
 			if (minion.id == null) {
 				minion.id = UUID.randomUUID().toString();
 			}