### Summary

The `apt_repository` will fail with a somewhat confusing error if gnugp, and dirmngr manager are not installed.  Neither of these packages are Required/Essential/Important, and may not be already installed in minimal systems that you might want to run `apt_repository` on.

The fix might be to just include `gnupg` in the requirements section of the docs.

### Issue Type

Documentation Report

### Component Name

apt_repository

### Ansible Version

```console
$  ansible --version
ansible [core 2.11.4]
  config file = ...
  configured module search path = ...
  ansible python module location = ...
  ansible collection location = ...
  executable location = /usr/local/bin/ansible
  python version = 3.9.2 (default, Feb 28 2021, 17:03:44) [GCC 10.2.1 20210110]
  jinja version = 3.0.1
  libyaml = True
```


### Configuration

```console
$ ansible-config dump --only-changed
```


### OS / Environment

Mostly a docs issue so this is N/A. But apt_repository applies to Debian, Ubuntu, and forks.

### Additional Information

Tells people that need gnupg when using apt_repository.

### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
valid = False
        enabled = True
        source = ''
        comment = ''
        line = line.strip()
        if line.startswith('#'):
            enabled = False
            line = line[1:]
        
        i = line.find('#')
        if i > 0:
            comment = line[i + 1:].strip()
            line = line[:i]
        
        
        source = line.strip()
        if source:
            chunks = source.split()
            if chunks[0] in VALID_SOURCE_TYPES:
                valid = True
                source = ' '.join(chunks)
        if raise_if_invalid_or_disabled and (not valid or not enabled):
            raise InvalidSource(line)
        return valid, enabled, source, comment
    @staticmethod
    def _apt_cfg_file(filespec):