[DOCS] Create includes note admonition in documentation referrencing GPG keys: GPG is used for all OpenPGP/PGP/GPG related material and implementations.

Description

GitLab seems to use GPG key as a standard in their documentation when it comes to OpenPGP/PGP/GPG related material and implementation references. GitLab also provides the following message about their docs:

The term GPG is used for all OpenPGP/PGP/GPG related material and implementations.

Our documentation may be referencing GPG keys, though technical correctness shows that GnuPG/GPG are open source, free alternatives to the PGP implementation. Searching for PGP, for example, could miss several docs that are using GPG in place of PGP.

Suggested Fix

Have an .. include:: of a reusable .. note:: admonition about the use of GPG in reference to OpenPGP/PGP/GPG.

Type of documentation

• Salt documentation
• Salt modules

Additional context

Originally posted by me in https://github.com/saltstack/salt/issues/59093#issuecomment-781568466 and is the source of creating this issue

That, or perhaps we can use PGP/GPG if they are meant to be interchangeable, allowing for both to appear when searching docs?

* correctness: `PGP`

* searchability: `PGP/GPG`

* compromise: `PGP/GnuPG`

I'm undecided :)

I'm thinking of leaving with gpg for now, due to much of configs and codebase making references to gpg keys:

egrep -rn "gpgkey|gpg_key"

Due to that, and with other docsets such as the GitHub, GitLab, and git docs as examples:

• GitHub Docs: Generating a New GPG Key
• git docs: Git Tools - Signing Your Work

If you have a GPG private key setup, you can now use it to sign new tags. All you have to do...

GitLab seems to use GPG key but also provides the following message about their docs:

The term GPG is used for all OpenPGP/PGP/GPG related material and implementations.

This seems important, because keys will be having -----BEGIN PGP SIGNATURE----- within them, too, to your point on technical correctness.

I'm going to go ahead and apply the commit suggestions I've made for GPG in the docs descriptions. I'm going to also create an issue to use GitLab's approach so that we can have an .. include:: of a reusable .. note:: admonition about the use of GPG in reference to OpenPGP/PGP/GPG.

Search the Salt documentation for existing GPG, PGP, or OpenPGP references and inspect how reusable includes and note admonitions are organized. Add the proposed shared note where appropriate across the Salt documentation and modules, then verify the affected documentation builds with the note rendered correctly.