Fix plugin docs (#3185)

* Fix plugin docs

* Add plugin_name to auth endpoint

website/source/api/system/auth.html.md

@@ -81,6 +81,9 @@ relevant functionality is only supported in Vault Enterprise:
   only. Local mounts are not replicated nor (if a secondary) removed by
   replication.
 
+- `plugin_name` `(string: "")` – Specifies the name of the auth plugin to
+  use based from the name in the plugin catalog.
+
 ### Sample Payload
 
 ```json

website/source/api/system/mounts.html.md

@@ -79,6 +79,7 @@ This endpoint mounts a new secret backend at the given path.
     - `default_lease_ttl`
     - `max_lease_ttl`
     - `force_no_cache`
+    - `plugin_name`
 
     These control the default and maximum lease time-to-live, and force
     disabling backend caching respectively. If set on a specific mount, this

website/source/api/system/plugins-backend-reload.html.md

@@ -43,5 +43,5 @@ This endpoint reloads mounted plugin backends.
 $ curl \
     --header "X-Vault-Token: ..." \
     --request PUT
-    https://vault.rocks/v1/sys/backends/reload
+    https://vault.rocks/v1/sys/plugins/backend/reload
 ```