mongodb: How to build facets from an array of objects

Question

What would be the best way to create facets from an array of objects with different attributes for each product.

Example Data:

[
  {
    "key": 1,
    "title": "Product A",
    "attrs": [
      {
        "keyasd": "size",
        "value": "small"
      },
      {
        "kedasy": "color",
        "value": "red"
      }
    ]
  },
  {
    "key": 2,
    "title": "Product B",
    "attrs": [
      {
        "key": "size",
        "value": "large"
      },
      {
        "key": "color",
        "value": "blue"
      }
    ]
  },
  {
    "key": 3,
    "title": "Product C",
    "attrs": [
      {
        "key": "resolution",
        "value": "8K"
      },
      {
        "key": "refresh rate",
        "value": "60 Hz"
      },
      
    ]
  }
]

The result I would like to get would be something like this:

[
    {
        "_id": {
            "key": "size",
            "values" : [
                {"title": "small", "count": 1},
                {"title": "large", "count": 1}
            ]
        }
    },
    {
        "_id": {
            "key": "color",
            "values" : [
                {"title": "red", "count": 1},
                {"title": "blue", "count": 1}
            ]
        }
    },
    {
        "_id": {
            "key": "resolution",
            "values" : [
                {"title": "8K", "count": 1}
            ]
        }
    },
    {
        "_id": {
            "key": "refresh rate",
            "values" : [
                {"title": "60 Hz", "count": 1}
            ]
        }
    }
]

I don't know if the result I put is possible, but I need to somehow build it, even if it's individually each facet for each type of attribute that a product can have