[Date Input Localization] Accept-Language Header Takes Precedence Over Language Set With Cookie

[blue-hexagon]

L10n Bug

Accept-Language Header takes precedence over language set with cookie when rendering date input form fields

This is a minimal example of a previously submitted bug - the original issue can be found here: https://code.djangoproject.com/ticket/34853

In the first example, the language and locale is set to en-US but the form fields are localized to da_DK. The docs make no mention that this should be the expected behaviour. I also show that output localizations, such as times and dates strings are localized properly as they should (see green text in images).

Expected formats:

• da_DK uses a dateformat of dd-MM-yyyy
• en_US uses a dateformat of mm/dd/yyyy

Please refer to the Github repository which contains a minimal example as well as the readme, which contains a full analysis with screenshot documentation and relevant highlights of settings, modelforms and models.

​https://github.com/blue-hexagon/dj-L10n_dateinput_bug

[blue-hexagon]

Rearrange a paragraph.

[Mariusz Felisiak]

Please don't open duplicates, instead add more details to the original ticket.

Duplicate of #34853.