Mongoose Validation আর Relationship

const productSchema = new Schema({
  name: { type: String, required: true, minlength: 2, maxlength: 100 },
  price: { type: Number, required: true, min: 0 },
  category: { type: String, enum: ["electronics", "books", "clothing"] }
})

const userSchema = new Schema({
  email: {
    type: String,
    required: true,
    validate: {
      validator: (value) => /^.+@.+\..+$/.test(value),
      message: "একটা বৈধ email address লিখুন"
    }
  }
})

const postSchema = new Schema({
  title: { type: String, required: true },
  author: { type: Schema.Types.ObjectId, ref: "User" }
})

const post = await Post.findOne({ title: "Getting Started" }).populate("author")
console.log(post.author.name)
// "Rahul Verma" — সম্পূর্ণ User document এখন attached