Makes guid optional in Relationship

cloudfoundry-client/src/main/java/org/cloudfoundry/client/v3/_Relationship.java

@@ -18,6 +18,7 @@
 
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+import org.cloudfoundry.Nullable;
 import org.immutables.value.Value;
 
 /**
@@ -31,6 +32,7 @@ abstract class _Relationship {
      * The id
      */
     @JsonProperty("guid")
+    @Nullable
     abstract String getId();
 
 }

cloudfoundry-client/src/test/java/org/cloudfoundry/client/v3/RelationshipTest.java

@@ -16,23 +16,24 @@
 
 package org.cloudfoundry.client.v3;
 
-import static org.junit.jupiter.api.Assertions.assertThrows;
-
 import org.junit.jupiter.api.Test;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 final class RelationshipTest {
 
     @Test
     void noId() {
-        assertThrows(
-                IllegalStateException.class,
-                () -> {
-                    Relationship.builder().build();
-                });
+        assertThat(Relationship.builder().build().getId()).isNull();
+    }
+
+    @Test
+    void nullId() {
+        assertThat(Relationship.builder().id(null).build().getId()).isNull();
     }
 
     @Test
-    void valid() {
-        Relationship.builder().id("test-id").build();
+    void nonNullId() {
+        assertThat(Relationship.builder().id("test-id").build().getId()).isEqualTo("test-id");
     }
 }

cloudfoundry-client/src/test/java/org/cloudfoundry/client/v3/domains/ShareDomainRequestTest.java

@@ -25,14 +25,10 @@ final class ShareDomainRequestTest {
 
     @Test
     void emptyRelationship() {
-        assertThrows(
-                IllegalStateException.class,
-                () -> {
-                    ShareDomainRequest.builder()
-                            .domainId("test-domain-id")
-                            .data(Relationship.builder().build())
-                            .build();
-                });
+        ShareDomainRequest.builder()
+                .domainId("test-domain-id")
+                .data(Relationship.builder().build())
+                .build();
     }
 
     @Test