docs: Update website to include SIGHUP, SIGTERM, and SIGINT behaviour (#3140)

* docs: Update website to include SIGHUP, SIGTERM, and SIGINT behaviour

Co-authored-by: Dan Heath <76443935+Dan-Heath@users.noreply.github.com>

website/content/docs/configuration/controller.mdx

@@ -106,6 +106,11 @@ description will be read.
   are anything specified by Go's [ParseDuration()](https://golang.org/pkg/time/#ParseDuration) method. Only
   used when an `ops` listener is set and the Controller is present. Default is 0 seconds.
 
+## Signals
+The `SIGHUP` signal causes a controller to reload its configuration file to pick up any updates to the `database url` value. Any other updated values are ignored.
+
+The `SIGTERM` and `SIGINT` signals initiate a graceful shutdown on a controller. A graceful shutdown closes listeners and servers before shutting down the controller.
+
 ## KMS Configuration
 
 The controller requires two KMS stanzas for `root` and `worker-auth` purposes:

website/content/docs/configuration/index.mdx

@@ -36,7 +36,7 @@ path to the file.
   Boundary serves traffic (API, cluster, and proxy).
 
   Controllers must have at least two listener blocks defined: one marked for
-  `api` purpose and the other marked for `cluster` purpose. 
+  `api` purpose and the other marked for `cluster` purpose.
 
   Workers will have only one listener, marked for `proxy` purpose.
 
@@ -87,6 +87,16 @@ path to the file.
 
 - [`plugins`](/boundary/docs/configuration/plugins): Configures options for plugins.
 
+## Signals
+The `SIGHUP` signal causes worker and controller processes to reload their configuration files to pick up updated values.
+
+~> **Note:** You cannot reload all configuration values using the `SIGHUP` signal. Refer to the configuration pages for
+[workers](/boundary/docs/configuration/worker/) and [controllers](/boundary/docs/configuration/controller) for details
+on which values can be reloaded on `SIGHUP`.
+
+The `SIGTERM` and `SIGINT` signals cause worker and controller processes to enter graceful shutdown. A graceful shutdown for a controller closes listeners and servers before shutting down the controller. A graceful shutdown for a worker waits for any sessions to drain
+before shutting down the worker. Workers in a graceful shutdown state do not receive any new work, including session proxying, from the control plane.
+
 ## Example Configurations
 
 For complete example configurations see the sections for

website/content/docs/configuration/worker/index.mdx

@@ -58,8 +58,8 @@ worker {
   at which the worker can be reached _by clients for proxying_. This defaults to
   the address of the listener marked for `proxy` purpose. This is especially
   useful for cloud environments that do not bind a publicly accessible IP to a
-  NIC on the host directly, such as an Amazon EIP. 
+  NIC on the host directly, such as an Amazon EIP.
-  
+
   This value can reference any of the following:
   - a direct address string
   - a file on disk (file://) from which an address will be read
@@ -85,6 +85,13 @@ worker {
   `initial_upstreams`. This is currently only valid for workers using the PKI
   registration method and for workers directly connected to HCP Boundary.
 
+## Signals
+The `SIGHUP` signal causes a worker to reload its configuration file to pick up any updates for the `initial_upstreams` and `tags` values.
+Any other updated values are ignored.
+
+The `SIGTERM` and `SIGINT` signals initiate a graceful shutdown on a worker. The worker waits for any sessions to drain
+before shutting down. Workers in a graceful shutdown state do not receive any new work, including session proxying, from the control plane.
+
 ## Multi-hop worker capabilities <sup>HCP only</sup>
 Multi-hop capabilities, including multi-hop sessions and Vault private access,
 is when a session or Vault credential request goes through more than one worker.