Add missing translations

Only consider order as overdue if order is open

Format according to Black

Use UTC in order overdue check

Unfortunately, freezegun seems not to make a difference here as the test
cases succeed with both `datetime.now()` and `datetime.utcnow()` in the
code under test.

Fix name of `self` argument in `Order.is_overdue`

Use slightly nicer gray for open order tags

Display order overdue flag in admin views

Display order overdue flag in site views

Introduce overdue flag to order transfer object

Use keyword arguments to populate shop article, order transfer objects

Move functions to create order (item) transfer objects from database models to order service

Change color of open shop order tags from red to yellow, waiting to ship from yellow to blue

Change color of initialized user tags from blue to yellow

Fix middot HTML entity unescaping in admin document titles

Remove database user model's unused `to_dto`

Avoid `to_dto`

Fix user avatar not shown in some views, avoid `to_dto`

Avoid and remove `find_active_db_user`

Use `get_db_user` for avatar update

Restriction to an active user is not strictly necessary here.

Introduce `get_detail`