Загрузить через FormData массив объектов

Пишу функцию создания товара . Мне нужно ,чтобы с помощью FormData при создании товара , товар был создан со списком пользователей . С одним пользователем мной уже было реализовано . Много чего мной было перепробовано для создания множественного выбора : 1) React-select, 2) Prime-React, 3) Стандартный HTML выбор (с атрибутом multiple) 4), React-multi-select-component , 5) multiselect-React-dropdown. Выдаёт одну и ту же ошибку : Product validation failed: partners.0: Cast to [ObjectId] failed for value "["6"]" (type string) at path "partners.0" . Прошу помочь и объяснить как с помощью FormData загрузить массив (в данном случае пользователей)

Форма создания товара:

    import React, { Fragment, useEffect, useState } from "react";
    import { useSelector, useDispatch } from "react-redux";
    import { clearErrors, createProduct } from "../../actions/productAction";
    import {loadAllUsers , clearCrashes} from "../../actions/userAction";
    import { useAlert } from "react-alert";
    import { Button } from "@material-ui/core";
    import MetaData from "../layout/MetaData";
    import AccountTreeIcon from "@material-ui/icons/AccountTree";
    import DescriptionIcon from "@material-ui/icons/Description";
    import StorageIcon from "@material-ui/icons/Storage";
    import SpellcheckIcon from "@material-ui/icons/Spellcheck";
    import AttachMoneyIcon from "@material-ui/icons/AttachMoney";
    import SideBar from "./Sidebar";
    import { NEW_PRODUCT_RESET } from "../../constants/productConstants";
    
    const NewProduct = ({ history }) => {
      const dispatch = useDispatch();
      const alert = useAlert();
    
      const { loading, error, success } = useSelector((state) => state.newProduct);
    
      const { crash , users } = useSelector((state) => state.allUsersLoad);
      
      const [title, setTitle] = useState("");
      const [price, setPrice] = useState(0);
      const [description, setDescription] = useState("");
      const [category, setCategory] = useState("");
      const [Stock, setStock] = useState(0);
      const [color , setcolor] = useState("");
      const [user , setuser] = useState("");
      const [partners , setpartners] = useState([])
      const [images, setImages] = useState([]);
      const [imagesPreview, setImagesPreview] = useState([]);
    
      const categories = [
        "Laptop",
        "Footwear",
        "Bottom",
        "Tops",
        "Attire",
        "Camera",
        "SmartPhones",
      ];
    
      const colors = ["Black" ,"Green","Grey","Red","Yellow","Brown" ,"White"];
    
      useEffect(() => {
        if (crash) {
          alert.error(crash);
          dispatch(clearCrashes());
        }
        dispatch(loadAllUsers());
      }, [dispatch, alert, crash]);
    
      useEffect(() => {
        if (error) {
          alert.error(error);
          dispatch(clearErrors());
        }
    
        if (success) {
          alert.success("Product Created Successfully");
          history.push("/admin/dashboard");
          dispatch({ type: NEW_PRODUCT_RESET });
        }
      }, [dispatch, alert, error, history, success]);
    
      const createProductSubmitHandler = (e) => {
        e.preventDefault();
    
        const myForm = new FormData();
    
        myForm.set("title", title);
        myForm.set("price", price);
        myForm.set("description", description);
        myForm.set("category", category);
        myForm.set("Stock", Stock);
        myForm.set("color", color);
        myForm.set("user", user);
    
        //partners.forEach((obj) =>{
         // Object.entries(obj).forEach((item , i) =>{
           // myForm.append("partners",`[${i}][${item[0]}]`); //??
         // })
       // })
      
       Object.values(partners).forEach(partner=>{
         myForm.append("partners", partner);  //??
       });
    
        images.forEach((image) => {
          myForm.append("images", image);
        });
        dispatch(createProduct(myForm));
      };
    
      const createProductImagesChange = (e) => {
        const files = Array.from(e.target.files);
    
        setImages([]);
        setImagesPreview([]);
    
        files.forEach((file) => {
          const reader = new FileReader();
    
          reader.onload = () => {
            if (reader.readyState === 2) {
              setImagesPreview((old) => [...old, reader.result]);
              setImages((old) => [...old, reader.result]);
            }
          };
    
          reader.readAsDataURL(file);
        });
      };
    
      return (
        <Fragment>
          <MetaData title="Create Product" />
          <div className="dashboard">
            <SideBar />
            <div className="newProductContainer">
              <form
                className="createProductForm"
                encType="multipart/form-data"
                onSubmit={createProductSubmitHandler}
              >
                <h1>Create Product</h1>
    
                <div>
                  <SpellcheckIcon />
                  <input
                    type="text"
                    placeholder="Product Title"
                    required
                    value={title}
                    onChange={(e) => setTitle(e.target.value)}
                  />
                </div>
                <div>
                  <AttachMoneyIcon />
                  <input
                    type="number"
                    placeholder="Price"
                    required
                    onChange={(e) => setPrice(e.target.value)}
                  />
                </div>
    
                <div>
                  <DescriptionIcon />
    
                  <textarea
                    placeholder="Product Description"
                    value={description}
                    onChange={(e) => setDescription(e.target.value)}
                    cols="30"
                    rows="1"
                  ></textarea>
                </div>
    
                <div>
                  <AccountTreeIcon />
                  <select onChange={(e) => setCategory(e.target.value)}>
                    <option value="">Choose Category</option>
                    {categories.map((cate) => (
                      <option key={cate} value={cate}>
                        {cate}
                      </option>
                    ))}
                  </select>
                </div>
    
                <div>
                  <StorageIcon />
                  <input
                    type="number"
                    placeholder="Stock"
                    required
                    onChange={(e) => setStock(e.target.value)}
                  />
                </div>
    
                <div>
                    <AccountTreeIcon />
                    <select onChange={(e) => setcolor(e.target.value)}>
                      <option value="">Choose Color</option>
                      {colors.map((co) => (
                      <option key={co} value={co}>
                        {co}
                      </option>
                      ))}
                    </select>
                  </div>
    
                  <div>
                    <AccountTreeIcon />
                    <select onChange={(e) => setuser(e.target.value)}>
                      <option value="">Choose User</option>
                         {users.map((us) => (
                      <option key={us._id} value={us._id}>
                        {us.name}
                      </option>
                      ))}
                    </select>
                  </div>
              <div>
                <AccountTreeIcon />  
                <select multiple onChange={(e) => {setpartners(e.target.value[0])}}>
                  <option value="">Choose Partners</option> //??
                     {users.map((us) => (
                  <option key={us._id} value={us._id}>
                    {us.name}
                  </option>
                  ))}
                </select>
              </div>

            <div id="createProductFormFile">
              <input
                type="file"
                name="avatar"
                accept="image/*"
                onChange={createProductImagesChange}
                multiple
              />
            </div>

            <div id="createProductFormImage">
              {imagesPreview.map((image, index) => (
                <img key={index} src={image} alt="Product Preview" />
              ))}
            </div>

            <Button
              id="createProductBtn"
              type="submit"
              disabled={loading ? true : false}
            >
              Create
            </Button>
          </form>
        </div>
      </div>
    </Fragment>
  );
};

export default NewProduct;

Модель товара:

сonst mongoose = require("mongoose");

const productSchema = mongoose.Schema({
  title: {
    type: String,
    required: [true, "Please Enter product Title"],
    trim: true,
  },
  description: {
    type: String,
    required: [true, "Please Enter product Description"],
  },
  price: {
    type: Number,
    required: [true, "Please Enter product Price"],
    maxLength: [8, "Price cannot exceed 8 characters"],
  },

  user: {
    type: mongoose.Schema.ObjectId,
    ref: "User",
    required: true,
  },

  partners: [
  {
      type: mongoose.Schema.ObjectId,
      ref: "User",
      required: true,
  }
],

  ratings: {
    type: Number,
    default: 0,
  },
  images: [
    {
      public_id: {
        type: String,
        required: true,
      },
      url: {
        type: String,
        required: true,
      },
    },
  ],

  category: {
    type: String,
    required: [true, "Please Enter Product Category"],
  },
  Stock: {
    type: Number,
    required: [true, "Please Enter product Stock"],
    maxLength: [4, "Stock cannot exceed 4 characters"],
    default: 1,
  },
  color: {
    type: String,
    default: "Not set!",
    enum: ["Black", "Green", "Grey", "Red", "Yellow","Brown","White"],
  },

  sold: {
    type: Number,
    trim: true,
    default: 0,
  },
  
  createdAt: {
    type: Date,
    default: Date.now,
  },
});

module.exports = mongoose.model("Product", productSchema);