### Summary

The [`filename` parameter docs](https://docs.ansible.com/ansible/latest/collections/ansible/builtin/apt_repository_module.html#parameter-filename) don't give enough info to tell how the file name is generated.

I believe my `repo: deb https://packagecloud.io/linz/prod/ubuntu/ {{ ansible_distribution_release }} main` is hanging indefinitely ~~, and I suspect this has something to do with the file name being a duplicate, resulting in a background prompt which is never printed or dismissed, but it's hard to tell based on the [code](https://github.com/ansible/ansible/blob/f3be331c9cb2f2c6edeb0bdf28a1e8a9681d727c/lib/ansible/modules/apt_repository.py#L235-L258)~~ (Based on copying the code into a Python interpreter it looks like the generated file name is `packagecloud_io_linz_prod_ubuntu.list`, which looks fine.).

### Issue Type

Documentation Report

### Component Name

lib/ansible/modules/apt_repository.py

### Ansible Version

```console
N/A
```


### Configuration

```console
N/A
```


### OS / Environment

N/A

### Additional Information

N/A

### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
else:
            
            module.fail_json(msg="{0} must be installed and visible from {1}.".format(apt_pkg_name, sys.executable))
    if not repo:
        module.fail_json(msg='Please set argument \'repo\' to a non-empty value')
    if isinstance(distro, aptsources_distro.Distribution):
        sourceslist = UbuntuSourcesList(module)
    else:
        module.fail_json(msg='Module apt_repository is not supported on target.')
    sourceslist_before = copy.deepcopy(sourceslist)
    sources_before = sourceslist.dump()
    try:
        if state == 'present':
            sourceslist.add_source(repo)
        elif state == 'absent':
            sourceslist.remove_source(repo)
    except InvalidSource as ex:
        module.fail_json(msg='Invalid repository string: %s' % to_native(ex))
    sources_after = sourceslist.dump()
    changed = sources_before != sources_after
    if changed and module._diff:
        diff = []
        for filename in set(sources_before.keys()).union(sources_after.keys()):
            diff.append({'before': sources_before.get(filename, ''),
                         'after': sources_after.get(filename, ''),
                         'before_header': (filename, '/dev/null')[filename not in sources_before],
                         'after_header': (filename, '/dev/null')[filename not in sources_after]})
    else:
        diff = {}