Rebalance strategy to seize best saving rate or best liquidity.

[dChef]

Design an automatic rebalance strategy - For example, when depositing X amount of USDT into dUSDT, the X will be distributed to different underlying lending protocols based on best saving interests. Considering gas consumption, the rebalancing should not be triggered upon every single deposit/withdraw action, there should be a range of internal pool acted as a buffer, say +- 5% (internal pool holds 10% underlying asset), so within 5%~15%, the rebalancing should not be trggered.