Add required id field to Spring Data Neo4j test class

Fixes gh-28303

Author: scottfrederick

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/data/neo4j/scan/TestRelationshipProperties.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,9 +16,15 @@
 
 package org.springframework.boot.autoconfigure.data.neo4j.scan;
 
+import org.springframework.data.neo4j.core.schema.GeneratedValue;
+import org.springframework.data.neo4j.core.schema.Id;
 import org.springframework.data.neo4j.core.schema.RelationshipProperties;
 
 @RelationshipProperties
 public class TestRelationshipProperties {
 
+	@Id
+	@GeneratedValue
+	Long id;
+
 }