allow config help in gateway mode (#9356)

allow `mc admin config set mygateway/ audit_webhook --env`
to fetch the documentation as needed, this is just to
ensure that our users can still access the relevant
ENV docs while running in gateway mode.

cmd/admin-router.go

@@ -88,13 +88,19 @@ func registerAdminRouter(router *mux.Router, enableConfigOps, enableIAMOps bool)
 			adminRouter.Methods(http.MethodGet).Path(adminVersion+"/get-config-kv").HandlerFunc(httpTraceHdrs(adminAPI.GetConfigKVHandler)).Queries("key", "{key:.*}")
 			adminRouter.Methods(http.MethodPut).Path(adminVersion + "/set-config-kv").HandlerFunc(httpTraceHdrs(adminAPI.SetConfigKVHandler))
 			adminRouter.Methods(http.MethodDelete).Path(adminVersion + "/del-config-kv").HandlerFunc(httpTraceHdrs(adminAPI.DelConfigKVHandler))
+		}
+
+		// Enable config help in all modes.
 		adminRouter.Methods(http.MethodGet).Path(adminVersion+"/help-config-kv").HandlerFunc(httpTraceAll(adminAPI.HelpConfigKVHandler)).Queries("subSys", "{subSys:.*}", "key", "{key:.*}")
+
+		// Config KV history operations.
+		if enableConfigOps {
 			adminRouter.Methods(http.MethodGet).Path(adminVersion+"/list-config-history-kv").HandlerFunc(httpTraceAll(adminAPI.ListConfigHistoryKVHandler)).Queries("count", "{count:[0-9]+}")
 			adminRouter.Methods(http.MethodDelete).Path(adminVersion+"/clear-config-history-kv").HandlerFunc(httpTraceHdrs(adminAPI.ClearConfigHistoryKVHandler)).Queries("restoreId", "{restoreId:.*}")
 			adminRouter.Methods(http.MethodPut).Path(adminVersion+"/restore-config-history-kv").HandlerFunc(httpTraceHdrs(adminAPI.RestoreConfigHistoryKVHandler)).Queries("restoreId", "{restoreId:.*}")
 		}
 
-		/// Config operations
+		/// Config import/export bulk operations
 		if enableConfigOps {
 			// Get config
 			adminRouter.Methods(http.MethodGet).Path(adminVersion + "/config").HandlerFunc(httpTraceHdrs(adminAPI.GetConfigHandler))