Migrate config to KV data format (#8392)

- adding oauth support to MinIO browser (#8400) by @kanagaraj
- supports multi-line get/set/del for all config fields
- add support for comments, allow toggle
- add extensive validation of config before saving
- support MinIO browser to support proper claims, using STS tokens
- env support for all config parameters, legacy envs are also
  supported with all documentation now pointing to latest ENVs
- preserve accessKey/secretKey from FS mode setups
- add history support implements three APIs
  - ClearHistory
  - RestoreHistory
  - ListHistory
- add help command support for each config parameters
- all the bug fixes after migration to KV, and other bug
  fixes encountered during testing.

cmd/storage-rest_test.go

@@ -24,6 +24,7 @@ import (
 	"testing"
 
 	"github.com/gorilla/mux"
+	"github.com/minio/minio/cmd/config"
 	xnet "github.com/minio/minio/pkg/net"
 )
 
@@ -488,7 +489,7 @@ func testStorageAPIRenameFile(t *testing.T, storage StorageAPI) {
 	}
 }
 
-func newStorageRESTHTTPServerClient(t *testing.T) (*httptest.Server, *storageRESTClient, *serverConfig, string) {
+func newStorageRESTHTTPServerClient(t *testing.T) (*httptest.Server, *storageRESTClient, config.Config, string) {
 	endpointPath, err := ioutil.TempDir("", ".TestStorageREST.")
 	if err != nil {
 		t.Fatalf("unexpected error %v", err)