fix: make space id to optional in move app api

src/main/java/com/kintone/client/AppClient.java

@@ -1403,11 +1403,21 @@ public GetViewsPreviewResponseBody getViewsPreview(GetViewsPreviewRequest reques
         return client.call(KintoneApi.GET_VIEWS_PREVIEW, request, handlers);
     }
 
+    /**
+     * Removes an App from its current Space.
+     *
+     * @param app the App ID
+     */
+    public void move(long app) {
+        move(app, null);
+    }
+
     /**
      * Changes the Space to which an App belongs.
      *
      * @param app the App ID
-     * @param space the Space ID of where the App will be moved to.
+     * @param space the Space ID of where the App will be moved to. If set to null, the App will be
+     *     removed from its current space.
      */
     public void move(long app, Long space) {
         MoveAppRequest req = new MoveAppRequest();
@@ -1420,8 +1430,7 @@ public void move(long app, Long space) {
      * Changes the Space to which an App belongs.
      *
      * @param request the request parameters. See {@link MoveAppRequest}
-     * @return the response data. To remove an App from its current space, null can be specified. See
-     *     {@link MoveAppResponseBody}
+     * @return the response data. See {@link MoveAppResponseBody}
      */
     public MoveAppResponseBody move(MoveAppRequest request) {
         return client.call(KintoneApi.MOVE_APP_TO_SPACE, request, handlers);

src/main/java/com/kintone/client/api/app/MoveAppRequest.java

@@ -11,8 +11,8 @@ public class MoveAppRequest implements KintoneRequest {
     private Long app;
 
     /**
-     * The Space ID of where the App will be moved to (required). To remove an App from its current
-     * space, null can be specified.
+     * The Space ID of where the App will be moved to (optional). If set to null or not set, the App
+     * will be removed from its current space.
      */
     private Long space;
 }

src/test/java/com/kintone/client/AppClientTest.java

@@ -1544,6 +1544,17 @@ public void getViewsPreview_GetViewsPreviewRequest() {
         assertThat(mockClient.getLastBody()).isEqualTo(req);
     }
 
+    @Test
+    public void moveToSpace_long() {
+        mockClient.setResponseBody(new MoveAppResponseBody());
+
+        sut.move(1);
+        assertThat(mockClient.getLastApi()).isEqualTo(KintoneApi.MOVE_APP_TO_SPACE);
+        assertThat(mockClient.getLastBody())
+                .usingRecursiveComparison()
+                .isEqualTo(new MoveAppRequest().setApp(1L).setSpace(null));
+    }
+
     @Test
     public void moveToSpace_long_long() {
         mockClient.setResponseBody(new MoveAppResponseBody());