The details of `regionendpoint` and `keyid` parameters when Amazon S3 is storage back-end

Issue

• regionendpoint parameter is what meaning in the Registry S3 storage configuration ?
• keyid parameter is what meaning in the Registry S3 storage configuration?
• storage section in Registry configuration.

storage:
  cache:
    layerinfo: inmemory
  delete:
    enabled: true
  s3:
    accesskey: awsaccesskey 
    secretkey: awssecretkey 
    region: us-west-1
    regionendpoint: http://myobjects.local
    bucket: bucketname
    encrypt: true
    keyid: mykeyid
    secure: true
    v4auth: false
    chunksize: 5242880
    rootdirectory: /s3/object/name/prefix