docs(worker): clarify Boundary worker registration workflows (#841)

* docs: clarify Boundary worker registration workflows

* update registration documentation wording

docs/resources/worker.md

@@ -21,6 +21,9 @@ resource "boundary_worker" "controller_led" {
 }
 ```
 
+Use controller-led registration when Terraform can deliver a generated activation
+token to the worker. Omit `worker_generated_auth_token`.
+
 ### Worker-led worker
 
 ```terraform
@@ -32,6 +35,34 @@ resource "boundary_worker" "worker_led" {
 }
 ```
 
+Use worker-led registration when the worker generates the authorization request.
+Set `worker_generated_auth_token` to the generated token.
+
+### No managed worker resource
+
+Without a `boundary_worker` resource, Terraform does not manage a worker.
+
+### Both registration methods
+
+Configure separate `boundary_worker` resources when your deployment requires
+both registration methods.
+
+```terraform
+resource "boundary_worker" "controller_led" {
+  scope_id = "global"
+  name     = "controller-led-worker-1"
+}
+
+resource "boundary_worker" "worker_led" {
+  scope_id                    = "global"
+  name                        = "worker-led-worker-1"
+  worker_generated_auth_token = var.worker_generated_auth_token
+}
+```
+
+Refer to the [register workers](https://developer.hashicorp.com/boundary/docs/workers/registration)
+documentation to learn about worker registration.
+
 <!-- schema generated by tfplugindocs -->
 ## Schema