Не удается сохранить один продукт (справочный массив) в другом документе (установка)?

Question

Я хочу сохранить только один продукт, используя один серийный номер, но не могу? Когда я сохраняю установку с продуктом, регистрируется весь массив продуктов. Как мне это сделать?

Это моя схема Proreg

const mongoose = require("mongoose");
const Schema = mongoose.Schema;

// Create Schema
const ProRegSchema = new Schema({
  refno1: {
    type: String
  },
  refno2: {
    type: String
  },
  date: {
    type: Date
  },
  customer: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "customer"
  },
  customertype: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "customertype"
  },
  department: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "customersubdepartment"
  },

  products: [
    {
      oem: {
        type: Schema.Types.ObjectId,
        ref: "company"
      },
      category: {
        type: mongoose.Schema.Types.ObjectId,
        ref: "productcategory"
      },
      subcategory: {
        type: mongoose.Schema.Types.ObjectId,
        ref: "productsubcategory"
      },
      modelno: {
        type: String
      },
      serialno: {
        type: String,
        required: true
      },
      warrantyfrom: {
        type: Date,
        default: "01-01-2019"
      },
      warrantyto: {
        type: Date,
        default: "01-01-2019"
      },
      oemwarrantyfrom: {
        type: Date,
        default: "01-01-2019"
      },
      oemwarrantyto: {
        type: Date,
        default: "01-01-2019"
      }
    }
  ],
  date: {
    type: Date,
    default: Date.now
  }
});

module.exports = ProReg = mongoose.model("proreg", ProRegSchema);

Это схема установки, где serialno будет именем свойства, которое сохранит только один продукт, полученный из схемы proreg.

const mongoose = require("mongoose");
const Schema = mongoose.Schema;

const InstallationSchema = new Schema({
  installrefno: { type: String },
  installdate: { type: Date },
  serialno: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "proreg"
  },
  installedby: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "employees"
  },

  customer: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "customer"
  },
  customertype: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "customertype"
  },
  department: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "customersubdepartment"
  },
  contactperson: { type: String },
  contactno: { type: Number },
  address: { type: String },
  remarks: { type: String },
  filename: { type: String },
  installdoc: { type: String }
});

module.exports = InstallationDetails = mongoose.model(
  "installation",
  InstallationSchema
);

Сначала я создаю Proreg, чтобы объяснить, как сохранить данные в Proreg

.

//ADD THE PROREG FIRST
router.post("/", (req, res) => {
  const newProReg = new ProReg({
    refno1: req.body.refno1,
    refno2: req.body.refno2,
    date: req.body.date,
    customer: req.body.customerid,
    customertype: req.body.customertypeid,
    department: req.body.customersubdepartmentid
  });

  newProReg.save().then(proreg => res.json(proreg));
});
//TAKE THE ID OF THE PROREG AND ADD THE PRODUCT
router.post("/product/:id", (req, res) => {
  ProReg.findById(req.params.id)
    .then(proreg => {
      const newProduct = {
        oem: req.body.companyid,
        category: req.body.productcategoryid,
        subcategory: req.body.productsubcategoryid,
        modelno: req.body.modelno,
        serialno: req.body.serialno,
        warrantyfrom: req.body.warrantyfrom,
        warrantyto: req.body.warrantyto,
        oemwarrantyfrom: req.body.oemwarrantyfrom,
        oemwarrantyto: req.body.oemwarrantyto
      };
      // Add to products array
      proreg.products.push(newProduct);

      // Save
      proreg.save().then(proreg => res.json(proreg));
    })
    .catch(err => res.status(404).json({ proregnotfound: "No pro reg found" }));
});

Это маршруты установки

 // Set The Storage Engine
    const storage = multer.diskStorage({
      destination: "client/public/install/docs",
      filename: function(req, file, cb) {
        cb(
          null,
          file.fieldname + "-" + Date.now() + path.extname(file.originalname)
        );
      }
    });

    const upload = multer({
      storage: storage,
      limits: {
        fileSize: 1024 * 1024 * 5
      }
    });
    //Create a new Installation Details
    router.post("/add", upload.single("installdoc"), (req, res, next) => {
      console.log(req.file);
      const newInstallationDetails = new InstallationDetails({
        installrefno: req.body.installrefno,
        installdate: req.body.installdate,
        serialno: req.body.productregistrationid,
        installedby: req.body.employeesid,
        customer: req.body.customerid,
        customertype: req.body.customertypeid,
        department: req.body.customersubdepartmentid,
        contactperson: req.body.contactperson,
        contactno: req.body.contactno,
        address: req.body.address,
        remarks: req.body.remarks,
        installdoc: req.file.path
      });
      newInstallationDetails.save().then(installation => res.json(installation));
    });

//And this is the routes where I access only the products using the serialno by bringing both the models Installation and product

        router.post("/selectone", (req, res) => {
      Installation.find()
        .then(inst => {
          //Take the exact serialno
          Proreg.find(
            { "products.serialno": req.body.serialno },

            //Match the exact serialno
            {
              products: {
                $elemMatch: { serialno: req.body.serialno }
              }
            }
          )

            .select("refno1")
            .select("refno2")
            .select("date")
            .populate("customer", "customername")
            .populate("customertype", "customertype")
            .populate("department", "department")
            //Populating the product nested array in object
            .populate("products.oem", "companyname")
            .populate("products.category", "category")
            .populate("products.subcategory", "subcategory")
            .then(inst => res.json(inst));
        })

        .catch(err => res.json(err));
    });

Когда я беру продукт регистрации и сохраняю его, он сохраняет все продукты, которые идут вместе с ним. Я хочу взять конкретный серийно, который сохранит только один продукт. Как мне это сделать в req.body серийно?