feat: Allow prefix and ip to be dynamically assigned

[amhn]

Fixes #45

This PR changes address and prefix to allow for automatic assignment.

Two caveats:

• Schema can not be validated with plan, since AtLeastOneOf does not support optional attributes. See https://github.com/hashicorp/terraform-plugin-sdk/issues/705. I don't know if this can be improved.
• Generation is not necessarily in order. Creating multiple prefixes at once will result in random ordering.

This PR needs https://github.com/smutel/go-netbox/pull/41 to be merged into go-netbox. After merging the lint failure should be gone.

[smutel]

https://github.com/smutel/go-netbox/releases/tag/v3.2.2

[smutel]

I think you need to rebase.

[amhn]

Done