Change default for new_generator_mappings to true

Closes gh-7612

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/orm/jpa/JpaProperties.java

@@ -202,7 +202,7 @@ public class JpaProperties {
 						this.useNewIdGeneratorMappings.toString());
 			}
 			else if (!result.containsKey(USE_NEW_ID_GENERATOR_MAPPINGS)) {
-				result.put(USE_NEW_ID_GENERATOR_MAPPINGS, "false");
+				result.put(USE_NEW_ID_GENERATOR_MAPPINGS, "true");
 			}
 		}
 

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/orm/jpa/JpaPropertiesTests.java

@@ -108,17 +108,17 @@ public class JpaPropertiesTests {
 		Map<String, String> hibernateProperties = properties
 				.getHibernateProperties(mockStandaloneDataSource());
 		assertThat(hibernateProperties)
-				.containsEntry(AvailableSettings.USE_NEW_ID_GENERATOR_MAPPINGS, "false");
+				.containsEntry(AvailableSettings.USE_NEW_ID_GENERATOR_MAPPINGS, "true");
 	}
 
 	@Test
-	public void useNewIdGeneratorMappingsTrue() throws Exception {
+	public void useNewIdGeneratorMappingsFalse() throws Exception {
 		JpaProperties properties = load(
-				"spring.jpa.hibernate.use-new-id-generator-mappings:true");
+				"spring.jpa.hibernate.use-new-id-generator-mappings:false");
 		Map<String, String> hibernateProperties = properties
 				.getHibernateProperties(mockStandaloneDataSource());
 		assertThat(hibernateProperties)
-				.containsEntry(AvailableSettings.USE_NEW_ID_GENERATOR_MAPPINGS, "true");
+				.containsEntry(AvailableSettings.USE_NEW_ID_GENERATOR_MAPPINGS, "false");
 	}
 
 	@Test