admin api: update v2 openapi spec

doc/api/garage-admin-v2.yml

@@ -4,6 +4,8 @@ info:
   title: Garage Administration API v0+garage-v2.0.0
   description: |
     Administrate your Garage cluster programatically, including status, layout, keys, buckets, and maintainance tasks.
+        
+    *Disclaimer: This API may change in future Garage versions. Read the changelog and upgrade your scripts before upgrading. Additionnaly, this specification is very early stage and can contain bugs, especially on error return codes/types that are not tested yet. Do not expect a well finished and polished product!*
 paths: 
   /GetClusterHealth:
     get:
@@ -194,7 +196,7 @@ paths:
           - Staged changes to the cluster layout
           
         *Capacity is given in bytes*
-        *The info returned by this endpoint is a subset of the info returned by `GET /status`.*
+        *The info returned by this endpoint is a subset of the info returned by `GET /GetClusterStatus`.*
       responses:
         '500':
           description: |