Private registry support for the CLI

The KubeClarity CLI can read a configuration file that stores credentials for private registries. (For details, on using an external configuration file, see Set configuration file location for the CLI).

Example registry section of the configuration file:

    - authority: <registry 1>
      username: <username for registry 1>
      password: <password for registry 1>
    - authority: <registry 2>
      token: <token for registry 2>

Example registry configuration without authority: (in this case these credentials will be used for all registries):

    - username: <username>
      password: <password>
Last modified October 16, 2023: Fix review comments (#7) (5b64ed8)