Add ISO Basic format support to datetime.isoformat() and date.isoformat()

Feature or enhancement

Proposal:

In additional to the popular ISO 8601 Extended format, there's also an ISO 8601 Basic format for datetimes which is useful for filenames and URL components as it avoids characters such as eg. colon and is more compact. datetime.fromisoformat already supports parsing this format.

Example code:

datetime.isoformat(basic=True)
# 20240422T204705.335-0400
date.isoformat(basic=True)
# 20240422

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-120553

首先審查連結的 PR gh-120553 以及現有的 datetime.isoformat() 和 date.isoformat() 入口點。確認針對 datetime 和 date 提出的 basic=True 範例，包括緊湊偏移量和不存在分隔符，並驗證所得行為已被涵蓋，然後再考慮將 issue 視為完成。