Consider requiring SSH key, disabling password delivery

[scop]

For security reasons.

Further constraints: https://developers.upcloud.com/1.3/8-servers/#creating-from-a-template

Additionally, it appears that the root password is stored by the module so that it can be retrieved in cleartext. This should be rectified in case we for some reason end up keeping the password login option.

[thevilledev]

This requires some internal refinement first

[thevilledev]

API docs for listing available templates: https://developers.upcloud.com/1.3/9-storages/#public-storages

In short:

• If the template has template_type: "cloud-init" only SSH keys can be utilised.
• If the template has template_type: "native" both SSH keys and one time passwords can be utilised.
• If the template does not have template_type defined, as with private templates, show both options. It's up to the template to either utilise cloud-init or alternatively pre-baked keys.

This should be reflected in the WHMCS module logic when defining these parameters.