Fix response of tobuy API

backend/src/main/java/com/example/todoapp/controller/ToBuysController.java

@@ -22,6 +22,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
+import java.util.Collections;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.http.ResponseEntity;
@@ -57,19 +58,19 @@ public class ToBuysController {
      */
 
     @PostMapping("/add")
-    public ResponseEntity<String> addToBuys(
+    public ResponseEntity<Map<String, Boolean>> addToBuys(
         @Valid @RequestBody ToBuysDTO dto, 
         Authentication authentication) {
         toBuysService.addToBuys(dto, authentication);
-        return ResponseEntity.ok("Item added to 'To Buys' successfully");
+        return ResponseEntity.ok(Collections.singletonMap("result", true));
     }
 
     @PutMapping("/update")
-    public ResponseEntity<String> updateToBuys(
+    public ResponseEntity<Map<String, Boolean>> updateToBuys(
         @Valid @RequestBody ToBuysDTO dto, 
         Authentication authentication) {
         toBuysService.updateToBuys(dto, authentication);
-        return ResponseEntity.ok("Item updated to 'To Buys' successfully");
+        return ResponseEntity.ok(Collections.singletonMap("result", true));
     }