docs: document root admin requirement for spacelift_space

The `spacelift_space` resource requires root space admin permissions to work. This means that it can only be used by administrative stacks that live in the root space.

I've added a note to the provider docs to make that more obvious.

docs/resources/space.md

@@ -4,12 +4,15 @@ page_title: "spacelift_space Resource - terraform-provider-spacelift"
 subcategory: ""
 description: |-
   spacelift_space represents a Spacelift space - a collection of resources such as stacks, modules, policies, etc. Allows for more granular access control. Can have a parent space.
+  Please note: the spacelift_space resource requires root Admin permissions, and can only be used by administrative stacks in the root space, or using an API key or user session that has root space access.
 ---
 
 # spacelift_space (Resource)
 
 `spacelift_space` represents a Spacelift **space** - a collection of resources such as stacks, modules, policies, etc. Allows for more granular access control. Can have a parent space.
 
+**Please note:** the `spacelift_space` resource requires root Admin permissions, and can only be used by administrative stacks in the root space, or using an API key or user session that has root space access.
+
 ## Example Usage
 
 ```terraform

spacelift/resource_space.go

@@ -17,7 +17,9 @@ import (
 func resourceSpace() *schema.Resource {
 	return &schema.Resource{
 		Description: "`spacelift_space` represents a Spacelift **space** - " +
-			"a collection of resources such as stacks, modules, policies, etc. Allows for more granular access control. Can have a parent space.",
+			"a collection of resources such as stacks, modules, policies, etc. Allows for more granular access control. Can have a parent space.\n\n" +
+			"**Please note:** the `spacelift_space` resource requires root Admin permissions, and can only be used by administrative stacks " +
+			"in the root space, or using an API key or user session that has root space access.",
 
 		CreateContext: resourceSpaceCreate,
 		ReadContext:   resourceSpaceRead,