feat: Support Signed-By option for apt repository

[tmccombs]

If it is used, it will avoid using the deprecated apt-key command.

Fixes: #13168

Description

Add support for a signed_by property for apt_repository.

If true, and a key is supplied, it will install the key in a repo-specific keyring, and reference that in the Signed-By option.
If a string, it will pass that string to the Signed-By option.

I'm not sure what the behavior should be if signed_by is a string, and a key is also supplied. Currently it will install the key in a repo-specific location, but use the value of the string in the signed-by field.

Other options for the case where key and signed-by are both specified could be:

1. install the key in /etc/apt/trusted.gpg.d, and use signed-by as is
2. try to interpret the first entry (comma seprated) as a file path, and install the key at that location
3. prepend the generated location to the list of signed-by values if it isn't already included

This still needs testing and documentation. But I wanted to see if this was a good approach before polishing it.

Related Issue

#13168

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (non-breaking change that does not add functionality or fix an issue)

Checklist:

• I have read the CONTRIBUTING document.
• I have run the pre-merge tests locally and they pass.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• If Gemfile.lock has changed, I have used --conservative to do it and included the full output in the Description above.
• All new and existing tests passed.
• All commits have been signed-off for the Developer Certificate of Origin.

[sonarqubecloud]

Quality Gate passed

The SonarCloud Quality Gate passed, but some issues were introduced.

5 New issues
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[sonarqubecloud]

Quality Gate passed

Issues
5 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[tpowell-progress]

If we can get this to non-draft and rebase on main we can restart the discussion about getting this folded in.

[schrd]

looks like some variable renamings have been missed

[sonarqubecloud]

Quality Gate passed

Issues
5 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[tpowell-progress]

@tmccombs can we get another rebase to validate that everything is working in the tests?

[sonarqubecloud]

Quality Gate passed

Issues
5 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud