feat: add value_as_string to avg/min/max/sum aggregations

[mcenkar]

min/max aggregations return also value_as_string, which can be useful when running over date fields:

{
  "aggregations": {
    "max-example": {
      "value": 1770336000000,
      "value_as_string": "2026-02-06"
    },
    "min-example": {
      "value": 1716422400000,
      "value_as_string": "2024-05-23"
    }
  }
}

It is possible to access them now.

[mcenkar]

Hi @Philippus,

appreciate if you could have a look at this PR. I can also add to avg or sum aggs, it makes less sense for me over dates, but others might find it useful.

[Philippus]

It would be awesome if you could add them for avg and sum as well. Would it also be possible to add some tests?

[mcenkar]

I updated PR + added some tests.

For avg and sum they are in separate tests (first, second) so more a bit more work but I can add them if you want.

(there is no value_as_string over numeric fields so would need to add date fields there as well)

[Philippus]

thanks!