Add deploy key functionality

[ZPascal]

The corresponding PR adds in general support for the SSH Key functionality and solve the following issue.

@ad-m Could we test the first version via a dev release? I want to consume the new dev release via this test job to validate the functionality.

[ad-m]

@ad-m Could we test the first version via a dev release?

You can, but this does not make sense in GitHub Actions, because you can always use commit SHA as a version identifier.

To use a specific action version, users can configure their GitHub Actions workflow to target a tag, a commit's SHA, or a branch named for a release.

Additionally, if you create a fork and push a commit into it, you can get each commit fork through the upstream repository: https://github.com/torvalds/linux/tree/8bcab0346d4fcf21b97046eb44db8cf37ddd6da0

[ad-m]

In practice, even some security-sensitive people recommend using SHA commit versions in GitHub Actions, because the tags do not guarantee immutability (you can delete the tag and create a new one, in effect injecting the code in all consumer of actions).

[ZPascal]

@ad-m Thanks, for detailed explanation! I’ve already tested it with the hash and everything works as expected and in I think in general the PR is now ready for a review.

[ad-m]

LGTM 👍🏼 Could you rebase & self-merge?