Challenge 3: Write a $jsonSchema Validator — Possible Solution
====================================================================

db.createCollection("products", {
  validator: {
    $jsonSchema: {
      bsonType: "object",
      required: ["name", "price"],
      properties: {
        name: { bsonType: "string" },
        price: { bsonType: ["double", "decimal"], minimum: 0 }
      }
    }
  }
})

WHY THIS WORKS AS AN ANSWER
------------------------------
Each requirement from the challenge maps onto a specific piece of the
validator, following the exact structure from this chapter's example:
  - required: ["name", "price"] ensures both fields must be present
    on every inserted/updated document — an insert missing either one
    is now rejected outright, restoring the enforcement a MySQL NOT
    NULL constraint would have provided by default.
  - name: { bsonType: "string" } constrains the name field's type.
  - price: { bsonType: [...], minimum: 0 } constrains price to be
    numeric AND non-negative — listing both "double" and "decimal" as
    acceptable bsonTypes is a reasonable real-world choice here, since
    per this chapter's own money guidance, a price field might
    legitimately be stored as Decimal128 rather than Double, and the
    validator shouldn't reject a well-considered Decimal128 price just
    because it happens not to be the default Double type.

This is the practical payoff of $jsonSchema: a collection that was
previously happy to accept any shape of document at all now enforces
the same two structural guarantees (required fields, correct types)
that a relational table's column definitions would have provided
automatically.