Manual backport 1.14.x of #17311 (#17355)

* [CC-4856] Add cloud stanza documentation

* Add environment variables to cloud descriptions

---------

Co-authored-by: Jeremy Jacobson <jeremy.jacobson@hashicorp.com>

website/content/docs/agent/config/config-files.mdx

@@ -1525,6 +1525,16 @@ Refer to the [formatting specification](https://golang.org/pkg/time/#ParseDurati
     part of the cluster before declaring it dead, giving that suspect node more time
     to refute if it is indeed still alive. The default is 6.
 
+## Self-managed HCP Parameters
+
+- `cloud` This object specifies settings for connecting self-managed clusters to HCP. This was added in Consul 1.14
+
+  - `client_id` The OAuth2 client ID for authentication with HCP. This can be overridden using the `HCP_CLIENT_ID` environment variable.
+
+  - `client_secret` The OAuth2 client secret for authentication with HCP. This can be overridden using the `HCP_CLIENT_SECRET` environment variable.
+
+  - `resource_id` The HCP resource identifier. This can be overridden using the `HCP_RESOURCE_ID` environment variable.
+
 ## Join Parameters
 
 - `rejoin_after_leave` Equivalent to the [`-rejoin` command-line flag](/docs/agent/config/cli-flags#_rejoin).