Fully consume insert response.

R2dbcEntityTemplate.insert(…) now fully consumes the response from the INSERT call before continuing. Previously, we consumed only the first signal and continued then. A driver could emit a row and then an error signal and so the error signal would go unnoticed.

Closes #552.

src/main/java/org/springframework/data/r2dbc/core/R2dbcEntityTemplate.java

@@ -392,8 +392,7 @@ public class R2dbcEntityTemplate implements R2dbcEntityOperations, BeanFactoryAw
 				.into(persistentEntity.getType()) //
 				.table(tableName).using(entityToInsert) //
 				.map(this.dataAccessStrategy.getConverter().populateIdIfNecessary(entityToInsert)) //
-				.first() //
-				.defaultIfEmpty(entityToInsert);
+				.all().last(entityToInsert); //
 	}
 
 	@SuppressWarnings("unchecked")