How to ensure all objects of an array are unique among documents in MongoDB

Question

We have a requirement for identifying (and avoid) duplicate records, which are contained inside of an Array of a parent document, ie:

{
  _id: 1,
  item: "abc",
  stock: [
    { size: "S", color: "red", quantity: 25 },
    { size: "S", color: "blue", quantity: 10 },
    { size: "M", color: "blue", quantity: 50 }
  ]
}
{
  _id: 2,
  item: "def",
  stock: [
    { size: "S", color: "blue", quantity: 25 },
    { size: "M", color: "blue", quantity: 5 },
    { size: "M", color: "black", quantity: 10 },
    { size: "L", color: "red", quantity: 2 }
  ]
}
{
  _id: 3,
  item: "ijk",
  stock: [
    { size: "S", color: "red", quantity: 25 },
    { size: "S", color: "blue", quantity: 10 },
    { size: "M", color: "blue", quantity: 50 }
  ]
}

In this example, items with _id: 1 and _id:3 are duplicate since all the elements of the array are exaclty the same

We have been trying to use the following reference but it does not take in consideration all the elements of the array as a whole but just a single property such as the color:

https://docs.mongodb.com/manual/core/index-multikey/#multikey-embedded-documents

If you have any other suggestion or workaround that could help us, we would very much appreciate it :)