Set initial_filesystem_type and initial_filesystem_label when reading volume resource

[mohsenSy]

closes #984

[andrewsomething]

Hi @mohsenSy, thanks for looking into this one. Unfortunately, it is a bit more complicated that this.

initial_filesystem_type and initial_filesystem_label are create time options that should not be set on read. They mean different things than filesystem_type and filesystem_label which are computed attributes that can change (e.g. the user re-formats the volume manually). There is some context in #136. We also need to support creating un-formatted volumes. As the API reports the current file system type, this would cause Terraform to try to recreate the volume once formatted.

We could potentially create a custom import function that sets them on import. Though that would effectively make them required on import. It would take some testing, by maybe a DiffSuppressFunc could work here? 🤔