anchor.diff:  -spec posix_model() -> maps:map().
   posix_model() ->
       #{
  +        %% The type of storage.
  +        type => {equal, <<"posix">>},
           %% The Id of storage.
           id => {string, optional},
           %% The name of storage.
  
positive.code:         username => string,
          %% The user role, one of `admin` or `regular`.
          userRole => atom,
          %% List of cluster privileges possessed by the user. This field is
          %% returned only to a Onezone user fetching information about himself.
          clusterPrivileges => {[string], optional}
      }.
  
  
negative.code: -spec ceph_model() -> maps:map().
  ceph_model() ->
      #{
          %% The type of storage.
          type => {equal, <<"ceph">>},
          %% The Id of storage.
          id => {string, optional},
          %% The name of storage.
  