Context based AccessKey passing (#10615)

A new field called AccessKey is added to the ReqInfo struct and populated.
Because ReqInfo is added to the context, this allows the AccessKey to be
accessed from 3rd-party code, such as a custom ObjectLayer.

Co-authored-by: Harshavardhana <harsha@minio.io>
Co-authored-by: Kaloyan Raev <kaloyan@storj.io>

cmd/logger/reqinfo.go

@@ -43,6 +43,7 @@ type ReqInfo struct {
 	API          string   // API name - GetObject PutObject NewMultipartUpload etc.
 	BucketName   string   // Bucket name
 	ObjectName   string   // Object name
+	AccessKey    string   // Access Key
 	tags         []KeyVal // Any additional info not accommodated by above fields
 	sync.RWMutex
 }