feat: replace ssh-private-key with ssh-private-keys and expected input is json with {name: key} entries.

[elvinristi]

Background

Module https://github.com/webfactory/ssh-agent exports public keys from private keys under .ssh/ folder and depends only on ssh-agent behaviour on selecting correct cert.

When trying to pass to docker build with action which doesn't support forwarded ssh-agent then while trying to use generated key-* files then we get invalid format - with PEM or non-PEM / reason is that public key can not be used for ssh-git authentication.

Description

With this change we export all passed private keys and use new format for input - object key should be "[email protected]:owner/repo.git" and we will use that one instead of trying to extract comment from public key where it potentially could be missing.

Example usage

      - name: Register SSH keys
        uses: vaimo/webfactory-ssh-agent-github@feature/json-private-keys--v2
        with:
          ssh-private-keys: |
              {
                "[email protected]:vaimo/vsf2--test-package.git": "${{ secrets.VAIMO_PRIVATE_REPO_TEST }}",
                "[email protected]:vaimo/vsf2_ext-lru-cache-driver": "${{ secrets.VAIMO_PRIVATE_REPO_LRU_DRV }}"
              }