### Summary

Based on feedback from a mastodon ansible user:

The first example of https://docs.ansible.com/ansible/latest/collections/ansible/builtin/apt_key_module.html#examples (the apt_key replacement) shows how a pgp key is downloaded and declared as trusted for a repository, but there is no validation of the key going on. Maybe the get_url task could include the checksum argument, to show that (and how) the key should be validated against a known good. Further down there is also an example of apt_key downloading a key without the id argument specified.

### Issue Type

Documentation Report

### Component Name

apt_key

### Ansible Version

```console
$ ansible --version
2.15
```


### Configuration

```console
# if using a version older than ansible-core 2.12 you should omit the '-t all'
$ ansible-config dump --only-changed -t all
none
```


### OS / Environment

none

### Additional Information

The examples all use https URLs, so they do not expose you to just arbitrary MITM; but many projects use untrusted public mirrors to distribute packages and public keys, and instead post the fingerprint of the public key on the non-mirrored first-party website. You are then supposed to verify the downloaded key against that fingerprint (unfortunately a manual action since they post a PGP fingerprint and not a checksum), in order to protect against rogue mirror operators (AFAIK).

### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
if keyring is not None:
        cmd = "%s --keyring %s adv --list-public-keys --keyid-format=long" % (apt_key_bin, keyring)
    else:
        cmd = "%s adv --list-public-keys --keyid-format=long" % apt_key_bin
    (rc, out, err) = module.run_command(cmd)
    if rc != 0:
        module.fail_json(msg="Unable to list public keys", cmd=cmd, rc=rc, stdout=out, stderr=err)
    return parse_output_for_keys(out, short_format)
def shorten_key_ids(key_id_list):
    """
    Takes a list of key ids, and converts them to the 'short' format,
    by reducing them to their last 8 characters.
    """
    short = []
    for key in key_id_list:
        short.append(key[-8:])
    return short
def download_key(module, url):