anchor.diff:          bucketName => string,
           %% The version of signature used to sign requests. One of: 2, 4.
           %% Default: 4.
  -        signatureVersion => {integer, optional},
  +        signatureVersion => {integer, {optional, 4}},
           %% Storage block size in bytes. In case the block size is `0`
           %% and `canonical` path type is selected, each file is stored
           %% in a single S3 object. This value must be set to `0` to
           %% enable data import from an existing S3 bucket.
  -        blockSize => {integer, optional},
  +        blockSize => {integer, {optional, 10485760}},
           %% Defines the maximum size for objects, which can be modified on the S3
           %% storage in `canonical` path mode. In this mode, entire file
           %% needs to be downloaded to memory, modified and uploaded back, which
  
positive.code:         %% Defines the file permissions, which files imported from S3 storage
          %% will have in Onedata. Values should be provided in octal format e.g.
          %% `0644`.
          fileMode => {string, optional},
          %% Defines the directory mode which directories imported from S3 storage
          %% will have in Onedata. Values should be provided in octal format e.g.
          %% `0775`.
          dirMode => {string, optional},
          %% Determines how the logical file paths will be mapped on the storage.
          %% 'canonical' paths reflect the logical file names and
          %% directory structure, however each rename operation will require
  
negative.code:         %% This field can contain any prefix that should be added to the header
          %% value. Default is `Authorization: Bearer {}`. The token
          %% will placed where `{}` is provided.
          authorizationHeader => {string, {optional, <<"Authorization: Bearer {}">>}},
          %% Defines the maximum number of parallel connections for a single HTTP
          %% storage.
          connectionPoolSize => {integer, {optional, 150}},
  