Brief audit of `rewards.ride`

[deemru]

• LOW: Complexity. Unnecessary constants calculations: https://github.com/Tsunami-Exchange/tsunami-contracts/blob/e761fd283558ee35caa73e34fb4c74653738263f/contracts/ride/rewards.ride#L37-L38
• TRIVIAL: Naming. Scaling up and down naming confusion: https://github.com/Tsunami-Exchange/tsunami-contracts/blob/e761fd283558ee35caa73e34fb4c74653738263f/contracts/ride/rewards.ride#L43-L44
• LOW: _balanceDelta is always 0. The code can be simplified in some places: https://github.com/Tsunami-Exchange/tsunami-contracts/blob/e761fd283558ee35caa73e34fb4c74653738263f/contracts/ride/rewards.ride#L126 https://github.com/Tsunami-Exchange/tsunami-contracts/blob/e761fd283558ee35caa73e34fb4c74653738263f/contracts/ride/rewards.ride#L139 https://github.com/Tsunami-Exchange/tsunami-contracts/blob/e761fd283558ee35caa73e34fb4c74653738263f/contracts/ride/rewards.ride#L144
• LOW: newRewardPerTokenStored is always newRewardPerTokenStored. The code can be simplified in some places: https://github.com/Tsunami-Exchange/tsunami-contracts/blob/e761fd283558ee35caa73e34fb4c74653738263f/contracts/ride/rewards.ride#L147
• LOW: newLastUpdateTime is always currentTimestampSec(). The code can be simplified in some places: https://github.com/Tsunami-Exchange/tsunami-contracts/blob/e761fd283558ee35caa73e34fb4c74653738263f/contracts/ride/rewards.ride#L146
• LOW: addRewards() is full duplicate of ackRewards() with payment. No reason to have addRewards() at all or at least the code can be combined.
• LOW: ackRewards() can be called automatically with other user functions to self update rewards distribution without backend interventions.
• LOW: Confused branch, actually it is the same branch with leftover = 0: https://github.com/Tsunami-Exchange/tsunami-contracts/blob/e761fd283558ee35caa73e34fb4c74653738263f/contracts/ride/rewards.ride#L312 https://github.com/Tsunami-Exchange/tsunami-contracts/blob/e761fd283558ee35caa73e34fb4c74653738263f/contracts/ride/rewards.ride#L316
• MEDIUM (debatable): Double fraction leads to dust accumulation on the contract (too often user calls for example withdrawRewards() can lead to user gets nothing in between): https://github.com/Tsunami-Exchange/tsunami-contracts/blob/e761fd283558ee35caa73e34fb4c74653738263f/contracts/ride/rewards.ride#L132 https://github.com/Tsunami-Exchange/tsunami-contracts/blob/e761fd283558ee35caa73e34fb4c74653738263f/contracts/ride/rewards.ride#L141