### 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
- This module supports Debian Squeeze (version 6) as well as its successors and derivatives.
options:
    repo:
        description:
            - A source string for the repository.
        type: str
        required: true
    state:
        description:
            - A source string state.
        type: str
        choices: [ absent, present ]
        default: "present"
    mode:
        description:
            - The octal mode for newly created files in sources.list.d.
            - Default is what system uses (probably 0644).
        type: raw
        version_added: "1.6"
    update_cache:
        description:
            - Run the equivalent of C(apt-get update) when a change occurs.  Cache updates are run after making changes.
        type: bool
        default: "yes"
        aliases: [ update-cache ]
    update_cache_retries:
        description:
        - Amount of retries if the cache update fails. Also see I(update_cache_retry_max_delay).
        type: int
        default: 5