anchor.diff:      C = #contract{ pubkey     = ContractPubKey,
                      balance    = aect_create_tx:amount(RTx),
                      height     = BlockHeight,
  +                   nonce      = 0,
                      %% Contract-specific fields
                      owner      = aect_create_tx:owner(RTx),
                      vm_version = aect_create_tx:vm_version(RTx),
  
positive.code: -spec height(contract()) -> height().
  height(C) -> C#contract.height.
  
  %% The owner of the contract is (initially) the account that created it.
  -spec owner(contract()) -> pubkey().
  owner(C) -> C#contract.owner.
  
negative.code:     [ {pubkey, Pubkey}
      , {balance, Balance}
      , {height, Height}
      , {nonce, Nonce}
      , {owner, Owner}
      , {vm_version, VmVersion}
      , {code, Code}
  