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.

pkg/event/config.go

@@ -167,6 +167,13 @@ func (q *Queue) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
 
 // Validate - checks whether queue has valid values or not.
 func (q Queue) Validate(region string, targetList *TargetList) error {
+	if q.ARN.region == "" {
+		if !targetList.Exists(q.ARN.TargetID) {
+			return &ErrARNNotFound{q.ARN}
+		}
+		return nil
+	}
+
 	if region != "" && q.ARN.region != region {
 		return &ErrUnknownRegion{q.ARN.region}
 	}