GH-2436 - Add RelationshipId as shortcut for relationship properties ids.

Closes #2436

Author: meistermeier

src/main/asciidoc/appendix/custom-queries.adoc

@@ -233,7 +233,7 @@ public final class Person {
 @RelationshipProperties
 public final class Actor {
 
-	@Id @GeneratedValue
+	@RelationshipId
 	private final Long id;
 
     @TargetNode

src/main/asciidoc/faq/faq.adoc

@@ -678,7 +678,7 @@ public final class Person {
 @RelationshipProperties
 public final class Actor {
 
-	@Id @GeneratedValue
+	@RelationshipId
 	private final Long id;
 
 	@TargetNode

src/main/asciidoc/object-mapping/mapping.adoc

@@ -223,14 +223,10 @@ A relationship property class and its usage may look like this:
 include::../../../../src/test/java/org/springframework/data/neo4j/documentation/domain/Roles.java[tags=mapping.relationship.properties]
 ----
 
-You must define a property for the generated, internal ID so that SDN can determine during save which relationships
+You must define a property for the generated, internal ID (`@RelationshipId`) so that SDN can determine during save which relationships
 can be safely overwritten without losing properties.
 If SDN does not find a field for storing the internal node id, it will fail during startup.
 
-NOTE: The only supported generated ID field on classes annotated with `@RelationshipProperties` is `@GeneratedValue` with
-      using the default ID generator `InternalIdGenerator` as shown above. Other generators will lead to a failure during
-      startup.
-
 .Defining relationship properties for an entity
 [source,java,indent=0]
 ----

src/main/java/org/springframework/data/neo4j/core/schema/GeneratedValue.java

@@ -39,7 +39,7 @@
  * @since 6.0
  */
 @Retention(RetentionPolicy.RUNTIME)
-@Target(ElementType.FIELD)
+@Target({ElementType.FIELD, ElementType.ANNOTATION_TYPE})
 @Documented
 @Inherited
 @API(status = API.Status.STABLE, since = "6.0")

src/main/java/org/springframework/data/neo4j/core/schema/Id.java

@@ -72,7 +72,7 @@
  * @since 6.0
  */
 @Retention(RetentionPolicy.RUNTIME)
-@Target(ElementType.FIELD)
+@Target({ElementType.FIELD, ElementType.ANNOTATION_TYPE})
 @Documented
 @Inherited
 @org.springframework.data.annotation.Id

src/main/java/org/springframework/data/neo4j/core/schema/RelationshipId.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2011-2021 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.neo4j.core.schema;
+
+import org.apiguardian.api.API;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Inherited;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * A combined annotation for id fields in {@link RelationshipProperties} classes.
+ *
+ * @author Gerrit Meier
+ * @since 6.2
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.FIELD)
+@Documented
+@Inherited
+@Id
+@GeneratedValue
+@API(status = API.Status.STABLE, since = "6.2")
+public @interface RelationshipId {
+}

src/test/java/org/springframework/data/neo4j/core/mapping/DefaultNeo4jPersistentEntityTest.java

@@ -40,6 +40,7 @@
 import org.springframework.data.neo4j.core.schema.Node;
 import org.springframework.data.neo4j.core.schema.Property;
 import org.springframework.data.neo4j.core.schema.Relationship;
+import org.springframework.data.neo4j.core.schema.RelationshipId;
 import org.springframework.data.neo4j.core.schema.RelationshipProperties;
 import org.springframework.data.neo4j.core.schema.TargetNode;
 
@@ -576,7 +577,7 @@ static class EntityWithInCorrectRelationshipProperties {
 	@RelationshipProperties
 	static class HasTargetNodeRelationshipProperties {
 
-		@Id @GeneratedValue
+		@RelationshipId
 		private Long id;
 
 		@TargetNode
@@ -586,7 +587,7 @@ static class HasTargetNodeRelationshipProperties {
 	@RelationshipProperties
 	static class HasNoTargetNodeRelationshipProperties {
 
-		@Id @GeneratedValue
+		@RelationshipId
 		private Long id;
 	}
 
@@ -650,7 +651,7 @@ static class OtherEntityWithBidirectionalRelationshipWithRelationshipProperties
 
 	@RelationshipProperties
 	static class OtherEntityWithBidirectionalRelationshipWithRelationshipPropertiesProperties {
-		@Id @GeneratedValue
+		@RelationshipId
 		private Long id;
 
 		@TargetNode
@@ -659,7 +660,7 @@ static class OtherEntityWithBidirectionalRelationshipWithRelationshipPropertiesP
 
 	@RelationshipProperties
 	static class EntityWithBidirectionalRelationshipWithRelationshipPropertiesProperties {
-		@Id @GeneratedValue
+		@RelationshipId
 		private Long id;
 
 		@TargetNode
@@ -683,7 +684,7 @@ static class EntityWithBidirectionalRelationshipProperties {
 	@RelationshipProperties
 	static class BidirectionalRelationshipProperties {
 
-		@Id @GeneratedValue
+		@RelationshipId
 		private Long id;
 
 		@TargetNode

src/test/java/org/springframework/data/neo4j/core/mapping/Neo4jMappingContextTest.java

@@ -61,6 +61,7 @@
 import org.springframework.data.neo4j.core.schema.Node;
 import org.springframework.data.neo4j.core.schema.Property;
 import org.springframework.data.neo4j.core.schema.Relationship;
+import org.springframework.data.neo4j.core.schema.RelationshipId;
 import org.springframework.data.neo4j.core.schema.RelationshipProperties;
 import org.springframework.data.neo4j.core.schema.TargetNode;
 import org.springframework.data.neo4j.integration.shared.common.FriendshipRelationship;
@@ -808,7 +809,7 @@ static class IrrelevantSourceContainer2 {
 
 	@RelationshipProperties
 	static class RelationshipPropertyContainer {
-		@Id @GeneratedValue @SuppressWarnings("unused")
+		@RelationshipId @SuppressWarnings("unused")
 		private Long id;
 
 		@TargetNode
@@ -896,8 +897,8 @@ public static class ConcreteEntity extends SomeBaseEntity {
 	}
 
 	public static class RelationshipPropertiesBaseClass<T extends SomeBaseEntity> {
-		@Id
-		@GeneratedValue
+
+		@RelationshipId
 		public Long internalId;
 
 		public String id;

src/test/java/org/springframework/data/neo4j/core/mapping/datagraph1446/AbstractR.java

@@ -15,8 +15,7 @@
  */
 package org.springframework.data.neo4j.core.mapping.datagraph1446;
 
-import org.springframework.data.neo4j.core.schema.GeneratedValue;
-import org.springframework.data.neo4j.core.schema.Id;
+import org.springframework.data.neo4j.core.schema.RelationshipId;
 import org.springframework.data.neo4j.core.schema.RelationshipProperties;
 import org.springframework.data.neo4j.core.schema.TargetNode;
 
@@ -27,7 +26,7 @@
 @RelationshipProperties
 public abstract class AbstractR<T> {
 
-	@Id @GeneratedValue
+	@RelationshipId
 	private Long id;
 
 	@TargetNode

src/test/java/org/springframework/data/neo4j/core/mapping/datagraph1448/R_S3.java

@@ -15,8 +15,7 @@
  */
 package org.springframework.data.neo4j.core.mapping.datagraph1448;
 
-import org.springframework.data.neo4j.core.schema.GeneratedValue;
-import org.springframework.data.neo4j.core.schema.Id;
+import org.springframework.data.neo4j.core.schema.RelationshipId;
 import org.springframework.data.neo4j.core.schema.RelationshipProperties;
 import org.springframework.data.neo4j.core.schema.TargetNode;
 
@@ -27,7 +26,7 @@
 @RelationshipProperties
 public class R_S3<T extends RelatedThing> {
 
-	@Id @GeneratedValue
+	@RelationshipId
 	private Long id;
 
 	@TargetNode