### 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
'''Simple iterator to go over all sources. Empty, non-source, and other not valid lines will be skipped.'''
        for file, sources in self.files.items():
            for n, valid, enabled, source, comment in sources:
                if valid:
                    yield file, n, enabled, source, comment
    def _expand_path(self, filename):
        if '/' in filename:
            return filename
        else:
            return os.path.abspath(os.path.join(self._apt_cfg_dir('Dir::Etc::sourceparts'), filename))
    def _suggest_filename(self, line):
        def _cleanup_filename(s):
            filename = self.module.params['filename']
            if filename is not None:
                return filename
            return '_'.join(re.sub('[^a-zA-Z0-9]', ' ', s).split())
        def _strip_username_password(s):
            if '@' in s:
                s = s.split('@', 1)
                s = s[-1]
            return s
        
        line = re.sub(r'\[[^\]]+\]', '', line)
        line = re.sub(r'\w+://', '', line)
        
        parts = [part for part in line.split() if part not in VALID_SOURCE_TYPES]
        
        parts[0] = _strip_username_password(parts[0])
        return '%s.list' % _cleanup_filename(' '.join(parts[:1]))
    def _parse(self, line, raise_if_invalid_or_disabled=False):