How to merge arrays and add key value as attribute in array items?

For the following input:

{
  "2024-10-10": {
    "item": [
      {
        "attr1": "a",
        "attr2": "b"
      },
      {
        "attr1": "c",
        "attr2": "d"
      }
    ]
  },
  "2025-10-10": {
    "item": [
      {
        "attr1": "e",
        "attr2": "f"
      }
    ]
  }
}

i'd like to get the output:

[
  {
    "attr1": "a",
    "attr2": "b",
    "date": "2024-10-10"
  },
  {
    "attr1": "c",
    "attr2": "d",
    "date": "2024-10-10"
  },
  {
    "attr1": "e",
    "attr2": "f",
    "date": "2025-10-10"
  }
]

For each object, the item array is merged, and new attribute date is added with the value from the top level. What Jolt transformation would work for this?

You can use the following shift transformation specs :

[
  {
    "operation": "shift",
    "spec": {
      "*": { //the level of the objects with date keys
        "item": {
          "*": { //for the indexes of the item array
            "*": "&3_&1.&", //separate by date and the indexes of the item array 
            "$2": "&3_&1.date" //bring date values from 3 upper levels,
                               //eg. indexed as 0,1,2(meaning $2)
          }
        }
      }
    }
  },
  { //get rid of the object keys
    "operation": "shift",
    "spec": {
      "*": "[]"
    }
  },
  { //sort alphabetically by the keys of the attributes
    "operation": "sort"
  }
]

the demo on the site Jolt Transform Demo Using v0.1.1 is :