__truediv__ to append a path drops final /

[mscout1]

Describe the bug

We have an internal api that cares about whether the url ends in a '/'.
This may be a poor design, but such things exist.

When a path is added to a url with the / operator, the final '/' is stripped.

import yarl
from yarl import URL
url = URL(f'http://example.com') / 'foo/bar/baz/'
print(url)

To Reproduce

from yarl import URL
url = URL(f'http://example.com') / 'foo/bar/baz/'
assert str(url).endswith('/'), "where did my slash go?"

url = URL(f'http://example.com') / 'foo' / 'bar'/ 'baz' / ''
assert str(url).endswith('/'), "still no slash?"

Expected behavior

The final slash should be preserved when appending a path with the truediv operator.
This would be in accord with the Principle of Least Surprise.

Logs/tracebacks

>>> from yarl import URL
>>> url = URL(f'http://example.com') / 'foo/bar/baz/'
>>> assert str(url).endswith('/'), "where did my slash go?"
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AssertionError: where did my slash go?
>>> 
>>> url = URL(f'http://example.com') / 'foo' / 'bar'/ 'baz' / ''
>>> assert str(url).endswith('/'), "still no slash?"
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AssertionError: still no slash?

Python Version

$ python --version
Python 3.11.4

multidict Version

$ python -m pip show multidict
Name: multidict
Version: 6.0.4
Summary: multidict implementation
Home-page: https://github.com/aio-libs/multidict
Author: Andrew Svetlov
Author-email: andrew.svetlov@gmail.com
License: Apache 2
Location: /home/matthew/venvs/wxp/lib/python3.11/site-packages
Requires: 
Required-by: aiohttp, yarl

yarl Version

$ python -m pip show yarl
Name: yarl
Version: 1.9.2
Summary: Yet another URL library
Home-page: https://github.com/aio-libs/yarl/
Author: Andrew Svetlov
Author-email: andrew.svetlov@gmail.com
License: Apache-2.0
Location: /home/matthew/venvs/wxp/lib/python3.11/site-packages
Requires: idna, multidict
Required-by: aio-pika, aiohttp, aiormq

OS

$ uname -a
Linux mattswxp 5.15.0-76-generic #83-Ubuntu SMP Thu Jun 15 19:16:32 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux

Additional context

No response

Code of Conduct

• I agree to follow the aio-libs Code of Conduct

[commonism]

Regression from 1.8.2

>>> yarl.__version__
'1.8.2'

>>> URL("https://example.inv/Foo/Bar/") / "test/"
URL('https://example.inv/Foo/Bar/test/')

"bi-sected" this to #704
@mjpieters want to assist?

[Dreamsorcerer]

So does pathlib though:

>>> print(pathlib.Path("foo") / "bar/baz/")
foo/bar/baz