[10] Launch Symbiotic Alchemix Pickle Jar

[larrythecucumber321]

Intro

Alchemix is a new DeFi protocol which allows for the creation of synthetic tokens representing future yield of a deposit. Essentially, a user can deposit DAI to mint alUSD, with the underlying DAI being invested in a yield-generating Yearn vault. ALCX is used to incentivize users who stake certain assets on their platform. For example, users who stake alUSD-3CRV Curve metapool tokens are rewarded with ALCX.

Alchemix has expressed a desire for Pickle to develop a symbiotic PickleJar for them. This is advantageous to Pickle for the cross-promotion opportunities and the high farming yields from which Pickle can earn fees.

Requirements

There are 2 Jars that we want developed for farming on top of Alchemix:

1. ALCX/ETH compounding LP Jar
2. alUSD-3CRV symbiotic Jar

1. ALCX/ETH

This one is straightforward - a user deposits ALCX/ETH Sushiswap LP tokens and we sell the earned ALCX rewards to increase the LP position in the Jar. An example strategy is the MIR-UST strategy here or in this PR #34.

2. alUSD-3CRV

This one is a bit more interesting in that it departs from our typical Jar strategy. The Jar strategy should work as follows:

1. accept deposits of alUSD-3CRV LP tokens
2. stake in Alchemix farm - this is an adaptation of masterchef
3. harvest ALCX rewards (from both the alUSD-3CRV and ALCX farms)
4. stake ALCX rewards (in the same farm contract above but with a different poolID). For reference, Yearn has developed their own ALCX staking strategy, but this doesn't need to be followed.

When users withdraw, they should receive their pro-rata share of alUSD-3CRV and ALCX tokens per their pToken balance.

Frontend

A new Jar and Farm should be added for both of these Jars on the frontend. Multiple examples can be found in our frontend repo.