BeethovenX token

Contracts

The token uses OpenZeppelins ERC20 base contract and only adds a maximum supply of 250mio BEETS to it.

The contract is based on SUSHI's version with some adjustments:

Upgrade to pragma 0.8.7
therefore remove usage of SafeMath (built in overflow check for solidity > 8)
Merge sushi's master chef V1 & V2 (no usage of dummy pool)
remove withdraw function (without harvest) => requires the rewardDebt to be an signed int instead of uint which requires a lot of casting and has no real usecase for us
no dev emissions, but treasury emissions instead
treasury percentage is subtracted from emissions instead of added on top
update of emission rate with upper limit of 6 BEETS/block
more require checks in general

Changes:

locking mechanism is based on epochs
an epoch is defined by the timestamp of the start of an epoch
an epoch length is defined by the epochDuration where the default is 1 week
there is an epoch for each week, there exist no holes (missing epochs)
the release time for a lock period is set to the current epoch + lockDuration which defaults to 17 weeks
all tokens locked within the same epoch share the same lock and therefore the same unlock time
withdrawal / re-locking is incentivized by paying a reward for kicking out expired locks (plus grace period)

locked tokens of the current epoch are not eligible for voting
locked tokens which are expired (lockDuration has passed) are not eligible for voting
the voting power is represented by the balanceOf function
the total voting power is represented by the totalSupply function

rewards are shared between users based on the total amount of locked tokens in the contract
tokens which have been locked in the current epoch and also tokens of expired locks are counted towards the total
rewards can be claimed at any time

Tests are located under the test/ directory.