dynamic host volumes: client configuration docs (#24827)

Document the client configuration changes needed to support dynamic host
volumes. This changeset excludes the plugin specification/concepts, which will
be under a separate PR.

Ref: #24797
Ref: https://hashicorp.atlassian.net/browse/NET-11482

Co-authored-by: Aimee Ukasick <[email protected]>
Co-authored-by: Daniel Bennett <[email protected]>

website/content/docs/configuration/client.mdx

@@ -201,6 +201,12 @@ client {
 - `host_volume` <code>([host_volume](#host_volume-block): nil)</code> - Exposes
   paths from the host as volumes that can be mounted into jobs.
 
+- `host_volume_plugin_dir` `(string: "")` - Specifies the directory to find host
+  volume plugins. When this parameter is empty, Nomad generates the path
+  using the [top-level `data_dir`][top_level_data_dir] suffixed with
+  `host_volume_plugins`, like `"/opt/nomad/host_volume_plugins"`. This must be
+  an absolute path.
+
 - `host_network` <code>([host_network](#host_network-block): nil)</code> - Registers
   additional host networks with the node that can be selected when port mapping.
 
@@ -613,11 +619,14 @@ see the [drivers documentation](/nomad/docs/drivers).
 
 ### `host_volume` Block
 
-The `host_volume` block is used to make volumes available to jobs.
+The `host_volume` block is used to make volumes available to jobs. You can also
+configure [dynamic host volumes][] via the [`volume create`][] or [`volume
+register`][] commands.
 
 The key of the block corresponds to the name of the volume for use in the
-`source` parameter of a `"host"` type [`volume`](/nomad/docs/job-specification/volume)
-and ACLs.
+`source` parameter of a `"host"` type
+[`volume`](/nomad/docs/job-specification/volume) and ACLs. A host volume in the
+configuration cannot have the same name as a dynamic host volume on the same node.
 
 ```hcl
 client {
@@ -807,3 +816,6 @@ client {
 [`TimeoutStopSec`]: https://www.freedesktop.org/software/systemd/man/systemd.service.html#TimeoutStopSec=
 [top_level_data_dir]: /nomad/docs/configuration#data_dir
 [unveil]: /nomad/docs/concepts/plugins/task-drivers#fsisolation-unveil
+[dynamic host volumes]: /nomad/docs/other-specifications/volume/host
+[`volume create`]: /nomad/docs/commands/volume/create
+[`volume register`]: /nomad/docs/commands/volume/register