Extend cli to create valid Gaia-X Credential for CSP

[anjastrunk]

Gaia-X requires a Gaia-X Credential for CSP, which can not be generated automatically as properties are not discoverable. Within the current implementation, these properties are provided by configuration file, which has to be updated manually. At very run, Gaia-X Credential for CSP is re-created resulting.

In favor of linked-data, it would be even better, if credential generator supports a CLI interface to create a Gaia-X Credential for CSP. It this, credential is generate once and can be re-used/referenced in other Gaia-X Credentials. During generation, CLI requests mandatory attributes from user.

[anjastrunk]

done by #96