Description of the problem, including code/CLI snippet

There is currently no way [or can't find one] to download a discussion/project upload, and it is supported by GitLab API.
I'm willing to work on that feature, although i might need some guidance on how you'd like to see it implemented :)

Expected Behavior

Ability to use something like:

attachment = project.get_upload(filename)

Actual Behavior

There is no way to download an upload, but there is possibility to upload new ones:
https://python-gitlab.readthedocs.io/en/stable/gl_objects/projects.html#file-uploads
https://docs.gitlab.com/ee/api/projects.html#download-an-uploaded-file

Specifications

• python-gitlab version: v4.10.0
• API version you are using (v3/v4): v4
• Gitlab server version (or gitlab.com): 17.3