filter datetime objects by date using __date

[xaptronic]

Add functionality to allow filtering for datetime type fields by date using {field_name}__date

Description

I have fields in my models/schema that are datetime objects, but I wish to be able to filter for them using only a date (e.g.; filter all entries on a particular date).

This PR adds __date operator that allows for such filtering.

Motivation and Context

There does not appear to be a way to filter datetime fields by a date object. Perhaps it can be done using lte / gte but I would rather specify one filter.. it seems more obvious and less of a work around a missing filter type.

How Has This Been Tested?

Added unit tests and used functionality in my use-case.

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added the changelog accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codspeed-hq]

CodSpeed Performance Report

Merging #1854 will not alter performance

_{Comparing xaptronic:develop (83cd816) with develop (e34c2c0)}

Summary

✅ 8 untouched benchmarks

[henadzit]

We should have more tests for these: checking that this filter modifier actually converts a date time to a date. The provided test case doesn't actually test anything. For instance, in Postgres

SELECT TIMESTAMP '2024-01-20 00:00:00' = DATE '2024-01-20';
> true

[henadzit]

Thanks for looking into this!

Here's a few links to how Django implements this:

• https://github.com/django/django/blob/22fc151bb86a553d84c62d7effd289356e9b6c6c/django/db/models/functions/datetime.py#L402
• Postgres implementation of datetime_cast_date_sql

In Django they implement the conversion for each database, so this might be more complicated than just using the Date function.