Implement Core Functionalities of StableSwap in Ralph

[polarker]

Objective
Implement the core functionalities of a StableSwap protocol within Ralph, focusing on creating a stable and efficient swapping mechanism for similarly-valued assets (e.g., stablecoins).

References
3Pool Code: https://github.com/curvefi/curve-contract/blob/master/contracts/pools/3pool/StableSwap3Pool.vy
Ralph Dex: https://github.com/alephium/alephium-dex/tree/master/contracts
StabeSwap white paper: https://berkeley-defi.github.io/assets/material/StableSwap.pdf

Scope of Work
Develop the following essential features for StableSwap:

1. Liquidity Pools

   • Enable users to deposit and withdraw assets into/from liquidity pools.
   • Ensure users can add multiple similarly-valued assets (e.g., stablecoins) into a single pool.
   • Implement a mechanism to track pool reserves and manage LP tokens for users.

2. Stable Swaps

   • Create a stable swap algorithm for low-slippage trades between similarly-valued assets.
   • Use an invariant function (e.g., constant product or similar stable swap algorithm) that maintains price stability during trades.

3. Fees & Incentives

   • Set up fee structures for swaps, which can be distributed to liquidity providers as incentives.
   • Implement adjustable parameters for fees to allow flexibility.

4. Yield Distribution

   • Allow the protocol to distribute fees collected from swaps to liquidity providers based on their share of the pool.
   • Calculate and periodically update yields for LP tokens held by liquidity providers.

Requirements

• Ensure modular and efficient code to support future scalability and upgrades.
• Maintain compatibility with Ralph’s existing architecture and standards.
• Include a comprehensive test suite covering unit tests, edge cases, and integration tests.