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/cache/config.go

@@ -28,9 +28,11 @@ import (
 
 // Config represents cache config settings
 type Config struct {
+	Enabled bool     `json:"-"`
 	Drives  []string `json:"drives"`
 	Expiry  int      `json:"expiry"`
 	MaxUse  int      `json:"maxuse"`
+	Quota   int      `json:"quota"`
 	Exclude []string `json:"exclude"`
 }
 
@@ -55,6 +57,10 @@ func (cfg *Config) UnmarshalJSON(data []byte) (err error) {
 		return errors.New("config max use value should not be null or negative")
 	}
 
+	if _cfg.Quota < 0 {
+		return errors.New("config quota value should not be null or negative")
+	}
+
 	if _, err = parseCacheDrives(_cfg.Drives); err != nil {
 		return err
 	}