I already integrated Vault and Jenkins and used it with Vault Username-Password Credential and now want to use the vault ssh username with private key type.
Here are my steps:
I generate private and public keys
Store the Public key on the GitLab itself
I want to Store the private key on Vault
Create the vault ssh username with private key credential and use it to connect to Gitlab (Instead of the old ssh username with private key)
If no-one has documented what configuration on the Vault side is expected for this feature of the Jenkins plugin, it might be that you have to track down the relevant source code and reverse engineer what it expects, or open a bug with the https://plugins.jenkins.io/hashicorp-vault-plugin/ project about this documentation gap.