Contracts pallet notes

[Centril]

Dumping some discussion notes for new contracts pallet here.

• State incentivation: Deposit based storage incentivation for pallet_contracts paritytech/substrate#9807
  • deposit = storage_used_before - storage_used_after
  • Add a deposit_limit field which limits how much balance is allowed to be deposited as part of the call.
• Add storage deposit, contracts: Add storage deposits paritytech/substrate#10082 [UNMERGED]
• State rent was removed in contracts: Remove state rent paritytech/substrate#9669 (september).
  • The biggest change is that the concept of a tombstone is gone.
  • The TombstoneDeposit is renamed to ContractDeposit and is a deposit a deployer needs to deposit into the new contract on top of the ExistentialDeposit (no change to the previous behavior).
• contracts: Allow contracts to dispatch calls into the runtime paritytech/substrate#9276

[Neopallium]

I like the idea of the caller paying for contract storage (with a refund if their call decreases storage usage).

One of the cons is that a contract can't use other financing options. But we could possibly allow a contract to refund or subsidize the transaction cost. The caller would still need to have enough POLYX to cover the transaction cost, since the contract has to run before it can decide if it is willing to pay for the cost.