Fixed pathlib bug for Windows by change to PurePosixPath

[lshaw8317]

Reproduce error:
import caterva2
public = caterva2.Root('@public', urlbase="https://cat2.cloud/demo")
print(public['examples/dir1/ds-2d.b2nd'])

Tries to request https://cat2.cloud/demo/api/info/@public\examples\dir1\ds-2d.b2nd (i.e with backslashes) and fails due to Windows file path convention. Fixed by forcing Unix-type (Posix) filepath naming.

[FrancescAlted]

Ok. Now we have this issue:

        if path is not None:
            p = path.as_posix() if isinstance(path, pathlib.Path) else path
>           if p.startswith("/"):
E           AttributeError: 'PurePosixPath' object has no attribute 'startswith'

Can you replace the code above by:

# Ensure path is a string before checking startswith
p = path.as_posix() if hasattr(path, "as_posix") else str(path)
if p.startswith("/"):

and see how it goes?

[lshaw8317]

Running on windows with following script
´´
import caterva2
public = caterva2.Root('@public', urlbase="https://cat2.cloud/demo")
print(public['examples/dir1/ds-2d.b2nd'])
``
incorrectly generated path and failed to find the server-hosted file. With bug fix suggested in commit, script now runs without error.

[FrancescAlted]

Looks good to me. Thanks @lshaw8317 !