feat(iaas): min/max acc tests (#811)

* feat(iaas): security group min/max acc test

* feat(iaas): image min/max acc test

* feat(iaas): KeyPair min/max acc test

* feat(iaas): Network area min/max acc test
- fix: wrong atLeast-validator for `minimum_prefix_length`

* feat(iaas): Network min/max acc test

* feat(iaas): Volume min/max acc test
- fix: volume update doesn't work if no name was defined
- fix: volume.server_id can not be set
- fix: error message volume.size returns value but was null

* feat(iaas): Network interfaces min/max acc test

* feat(iaas): Affinity groups acc test

* feat(iaas): Server min/max acc test
- stackit_server_volume_attach
- stackit_server_network_interface_attach
- stackit_server_service_account_attach

* fix(iaas): acc test
- image: fix read of Config.VirtioScsi
- keypair: add missing RequiresReplace() for name
- server: add missing UserData read in datasource and resource

* feat(iaas): public ip acc test
- fix: when a nic is assigned to a public ip, the field network_interface_id leads to recreation

Author: marceljk

docs/resources/volume.md

@@ -38,13 +38,13 @@ resource "stackit_volume" "example" {
 - `labels` (Map of String) Labels are key-value string pairs which can be attached to a resource container
 - `name` (String) The name of the volume.
 - `performance_class` (String) The performance class of the volume. Possible values are documented in [Service plans BlockStorage](https://docs.stackit.cloud/stackit/en/service-plans-blockstorage-75137974.html#ServiceplansBlockStorage-CurrentlyavailableServicePlans%28performanceclasses%29)
-- `server_id` (String) The server ID of the server to which the volume is attached to.
 - `size` (Number) The size of the volume in GB. It can only be updated to a larger value than the current size. Either `size` or `source` must be provided
 - `source` (Attributes) The source of the volume. It can be either a volume, an image, a snapshot or a backup. Either `size` or `source` must be provided (see [below for nested schema](#nestedatt--source))
 
 ### Read-Only
 
 - `id` (String) Terraform's internal resource ID. It is structured as "`project_id`,`volume_id`".
+- `server_id` (String) The server ID of the server to which the volume is attached to.
 - `volume_id` (String) The volume ID.
 
 <a id="nestedatt--source"></a>