Convert empty or blank name to non-blank in readResolve

Jenkins 2.403 improves the cloud management user interface.  Each cloud is
now managed from a separate page.  That separate page requires a non-blank
name for the cloud.  Jenkins 2.402 and later allowed a blank name.

When a blank name is detected, convert it to a non-blank name based on
the hashCode of the DockerAPI and templates.

src/main/java/com/nirima/jenkins/plugins/docker/DockerCloud.java

@@ -143,6 +143,13 @@ public DockerCloud(String name, DockerAPI dockerApi, List<DockerTemplate> templa
         }
     }
 
+    /* Constructor to create a new DockerCloud based on an existing DockerCloud */
+    public DockerCloud(@NonNull String name, @NonNull DockerCloud source) {
+        super(name);
+        this.dockerApi = source.dockerApi;
+        this.templates = source.templates;
+    }
+
     @Deprecated
     public DockerCloud(
             String name,
@@ -731,7 +738,9 @@ protected Object readResolve() {
         }
 
         if (name == null || name.isBlank()) {
-            LOGGER.warn("Docker cloud requires a non-blank name after Jenkins 2.402");
+            String newName = "docker-cloud-" + Integer.toHexString(hashCode());
+            LOGGER.warn("Docker cloud requires a non-blank name after Jenkins 2.402, using '" + newName + "'");
+            return new DockerCloud(newName, this);
         }
 
         return this;

src/test/java/com/nirima/jenkins/plugins/docker/DockerCloudTest.java

@@ -78,6 +78,21 @@ public void testConstructorWithNullName() {
         MatcherAssert.assertThat(lr.getMessages(), IsIterableContaining.hasItem(LOG_MESSAGE));
     }
 
+    @Issue("JENKINS-70729") // Handle null or empty cloud name
+    @Test
+    public void testCopyConstructor() {
+        lr.record(DockerCloud.class.getName(), Level.ALL).capture(16);
+        DockerCloud cloud =
+                new DockerCloud(null, new DockerAPI(new DockerServerEndpoint("uri", "credentialsId")), List.of());
+        Assert.assertEquals(cloud.getDisplayName(), null);
+        MatcherAssert.assertThat(lr.getMessages(), IsIterableContaining.hasItem(LOG_MESSAGE));
+        String newName = "docker-cloud-" + Integer.toHexString(cloud.hashCode());
+        DockerCloud copy = new DockerCloud(newName, cloud);
+        Assert.assertEquals(cloud.getDockerApi(), copy.getDockerApi());
+        Assert.assertEquals(cloud.getTemplates().hashCode(), copy.getTemplates().hashCode());
+        Assert.assertEquals(newName, copy.getDisplayName());
+    }
+
     @Test
     public void globalConfigRoundtrip() throws Exception {