Move admin APIs to new path and add redesigned heal APIs (#5351)

- Changes related to moving admin APIs
   - admin APIs now have an endpoint under /minio/admin
   - admin APIs are now versioned - a new API to server the version is
     added at "GET /minio/admin/version" and all API operations have the
     path prefix /minio/admin/v1/<operation>
   - new service stop API added
   - credentials change API is moved to /minio/admin/v1/config/credential
   - credentials change API and configuration get/set API now require TLS
     so that credentials are protected
   - all API requests now receive JSON
   - heal APIs are disabled as they will be changed substantially

- Heal API changes
   Heal API is now provided at a single endpoint with the ability for a
   client to start a heal sequence on all the data in the server, a
   single bucket, or under a prefix within a bucket.

   When a heal sequence is started, the server returns a unique token
   that needs to be used for subsequent 'status' requests to fetch heal
   results.

   On each status request from the client, the server returns heal result
   records that it has accumulated since the previous status request. The
   server accumulates upto 1000 records and pauses healing further
   objects until the client requests for status. If the client does not
   request any further records for a long time, the server aborts the
   heal sequence automatically.

   A heal result record is returned for each entity healed on the server,
   such as system metadata, object metadata, buckets and objects, and has
   information about the before and after states on each disk.

   A client may request to force restart a heal sequence - this causes
   the running heal sequence to be aborted at the next safe spot and
   starts a new heal sequence.

cmd/object-api-datatypes.go

@@ -50,21 +50,6 @@ type StorageInfo struct {
 	}
 }
 
-type healStatus int
-
-const (
-	healthy           healStatus = iota // Object is healthy
-	canHeal                             // Object can be healed
-	corrupted                           // Object can't be healed
-	quorumUnavailable                   // Object can't be healed until read quorum is available
-	canPartiallyHeal                    // Object can't be healed completely until outdated disk(s) are online.
-)
-
-// HealBucketInfo - represents healing related information of a bucket.
-type HealBucketInfo struct {
-	Status healStatus
-}
-
 // BucketInfo - represents bucket metadata.
 type BucketInfo struct {
 	// Name of the bucket.
@@ -72,16 +57,6 @@ type BucketInfo struct {
 
 	// Date and time when the bucket was created.
 	Created time.Time
-
-	// Healing information
-	HealBucketInfo *HealBucketInfo `xml:"HealBucketInfo,omitempty"`
-}
-
-// HealObjectInfo - represents healing related information of an object.
-type HealObjectInfo struct {
-	Status             healStatus
-	MissingDataCount   int
-	MissingParityCount int
 }
 
 // ObjectInfo - represents object metadata.
@@ -113,8 +88,7 @@ type ObjectInfo struct {
 	ContentEncoding string
 
 	// User-Defined metadata
-	UserDefined    map[string]string
-	HealObjectInfo *HealObjectInfo `xml:"HealObjectInfo,omitempty"`
+	UserDefined map[string]string
 }
 
 // ListPartsInfo - represents list of all parts.
@@ -273,8 +247,6 @@ type MultipartInfo struct {
 	Initiated time.Time
 
 	StorageClass string // Not supported yet.
-
-	HealUploadInfo *HealObjectInfo `xml:"HealUploadInfo,omitempty"`
 }
 
 // CompletePart - represents the part that was completed, this is sent by the client