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/logger/legacy.go

@@ -0,0 +1,54 @@
+/*
+ * MinIO Cloud Storage, (C) 2019 MinIO, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package logger
+
+import "github.com/minio/minio/cmd/config"
+
+// Legacy envs
+const (
+	EnvAuditLoggerHTTPEndpoint = "MINIO_AUDIT_LOGGER_HTTP_ENDPOINT"
+)
+
+// SetLoggerHTTPAudit - helper for migrating older config to newer KV format.
+func SetLoggerHTTPAudit(scfg config.Config, k string, args HTTP) {
+	scfg[config.LoggerHTTPAuditSubSys][k] = config.KVS{
+		config.State: func() string {
+			if args.Enabled {
+				return config.StateOn
+			}
+			return config.StateOff
+		}(),
+		config.Comment: "Settings for HTTP Audit logging, after migrating config",
+		Endpoint:       args.Endpoint,
+		AuthToken:      args.AuthToken,
+	}
+}
+
+// SetLoggerHTTP helper for migrating older config to newer KV format.
+func SetLoggerHTTP(scfg config.Config, k string, args HTTP) {
+	scfg[config.LoggerHTTPSubSys][k] = config.KVS{
+		config.State: func() string {
+			if args.Enabled {
+				return config.StateOn
+			}
+			return config.StateOff
+		}(),
+		config.Comment: "Settings for HTTP logging, after migrating config",
+		Endpoint:       args.Endpoint,
+		AuthToken:      args.AuthToken,
+	}
+}