docs: update primary ip arguments requirements (#1017)

Co-authored-by: jo <[email protected]>

website/docs/r/primary_ip.html.md

@@ -50,22 +50,23 @@ resource "hcloud_server" "server_test" {
 - `auto_delete` - (bool) Whether auto delete is enabled.
   `Important note:`It is recommended to set `auto_delete` to `false`, because if a server assigned to the managed ip is getting deleted, it will also delete the primary IP which will break the TF state.
 - `labels` - (map, optional) User-defined labels (key-value pairs).
-- `assignee_id` - (int) ID of the assigned resource
+- `assignee_id` - (int, optional) ID of the assigned resource.
 - `assignee_type` - (string) The type of the assigned resource. Currently supported: `server`
-- `delete_protection` - (bool) Whether delete protection is enabled. See ["Delete Protection"](../index.html.markdown#delete-protection) in the Provider Docs for details.
+- `delete_protection` - (bool, optional) Whether delete protection is enabled. See ["Delete Protection"](../index.html.markdown#delete-protection) in the Provider Docs for details.
+
+Note: At least one of `datacenter` or `assignee_id` is required.
 
 ## Attributes Reference
 
 - `id` - (int) Unique ID of the Primary IP.
 - `type` - (string) Type of the Primary IP.
-- `datacenter` - (string, optional) The datacenter name to create the resource in.
+- `datacenter` - (string) The datacenter of the Primary IP.
 - `name` - (string) Name of the Primary IP.
 - `auto_delete` - (bool) Whether auto delete is enabled.
-  `Important note:`It is recommended to set `auto_delete` to `false`, because if a server assigned to a managed ip is getting deleted, it will also delete the primary IP which will break the TF state.
 - `labels` - (map) User-defined labels (key-value pairs).
 - `ip_address` - (string) IP Address of the Primary IP.
 - `ip_network` - (string) IPv6 subnet of the Primary IP for IPv6 addresses. (Only set if `type` is `ipv6`)
-- `assignee_id` - (int) ID of the assigned resource
+- `assignee_id` - (int) ID of the assigned resource.
 - `assignee_type` - (string) The type of the assigned resource.
 - `delete_protection` - (bool) Whether delete protection is enabled.