[x/gamm]: Add RPC query endpoints for joining and exiting pools

[georgemc98]

Background

It would be helpful to have a RPC query that returns the lp shares when providing liquidity to a pool. It would also be helpful to have a query that returns the assets returned withdrawing liquidity from a liquidity pool. These queries will be useful when using a StargateQuery in cosmwasm smart contracts.

Suggested Design

Here is the commit for the PoolType query that was added recently: e55e13d. The design should follow the steps taken in this commit to add RPC end points for the four following queries:

• QueryJoinPool
  • Parameters: QueryJoinPoolSharesRequest{ PoolId, TokenInMaxs}
  • Returns: QueryJoinPoolSharesResponse { ShareOutAmount, TokenIn }
• QueryJoinSwapExactAmountIn
  • Parameters: QueryJoinSwapExactAmountInRequest{ PoolId, TokenIn}
  • Returns: QueryJoinSwapExactAmountInResponse { ShareOutAmount }
• QueryExitPool
  • Parameters: QueryExitPoolSharesRequest{ PoolId, ShareInAmount }
  • Returns: QueryExitPoolSharesResponse { TokenOut }
• QueryExitSwapShareAmountIn
  • Parameters: QueryExitSwapShareAmountInRequest{ PoolId, TokenOutDenom, ShareInAmount }
  • Returns: QueryExitSwapShareAmountInResponse { TokenOutAmount }

[pysel]

I would like to work on this issue!

[georgemc98]

I would like to work on this issue!

Excellent. I am going to start on QueryJoinPool and QueryExitPool today.