Updated staking smart contract lineup

Single-nominator (v1.1) — Direct validation with one validator and one nominator. The nominator receives 100% of the rewards.

Nominator-pool (v2) — Private staking pools with a small group of nominators and validators.

Liquid-staking — User-facing staking products with many depositors. Issues jettons representing staked Gram for use in DeFi. Used by @StakeeBot and Tonstakers.