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/config-migrate_test.go

@@ -21,6 +21,8 @@ import (
 	"io/ioutil"
 	"os"
 	"testing"
+
+	"github.com/minio/minio/cmd/config"
 )
 
 // Test if config v1 is purged
@@ -208,24 +210,24 @@ func TestServerConfigMigrateV2toV33(t *testing.T) {
 		t.Fatal("Unexpected error: ", err)
 	}
 
+	if err := migrateMinioSysConfigToKV(objLayer); err != nil {
+		t.Fatal("Unexpected error: ", err)
+	}
+
 	// Initialize server config and check again if everything is fine
 	if err := loadConfig(objLayer); err != nil {
 		t.Fatalf("Unable to initialize from updated config file %s", err)
 	}
 
-	// Check the version number in the upgraded config file
-	expectedVersion := serverConfigVersion
-	if globalServerConfig.Version != expectedVersion {
-		t.Fatalf("Expect version "+expectedVersion+", found: %v", globalServerConfig.Version)
-	}
-
 	// Check if accessKey and secretKey are not altered during migration
-	if globalServerConfig.Credential.AccessKey != accessKey {
-		t.Fatalf("Access key lost during migration, expected: %v, found:%v", accessKey, globalServerConfig.Credential.AccessKey)
+	caccessKey := globalServerConfig[config.CredentialsSubSys][config.Default][config.AccessKey]
+	if caccessKey != accessKey {
+		t.Fatalf("Access key lost during migration, expected: %v, found:%v", accessKey, caccessKey)
 	}
 
-	if globalServerConfig.Credential.SecretKey != secretKey {
-		t.Fatalf("Secret key lost during migration, expected: %v, found: %v", secretKey, globalServerConfig.Credential.SecretKey)
+	csecretKey := globalServerConfig[config.CredentialsSubSys][config.Default][config.SecretKey]
+	if csecretKey != secretKey {
+		t.Fatalf("Secret key lost during migration, expected: %v, found: %v", secretKey, csecretKey)
 	}
 }