Decide on whether or not to combine initial and bonus multiplier points in max MP calculation

[0x-r4bbit]

Currently, the maximum possible multiplier points amount for any account is calculated based on:

https://github.com/logos-co/staking/blob/4f590049d4cf79706dca86df20f3c0903c92ac95/contracts/StakeManager.sol#L416-L435

Specifically this line:

https://github.com/logos-co/staking/blob/4f590049d4cf79706dca86df20f3c0903c92ac95/contracts/StakeManager.sol#L427

_initialMP is always going to be the initial multiplier points minted via the balance amount when staking, in addition to the bonus multiplier points for the stake lockup time.

This results in the maximum multiplier points to be more than what's currently described in the docs

Maximum MP = staked SNT * maximum_MP_multiplier

The reason it was done that like in the current code is because if a lockup time is high enough, an account would immediately hit the max boost sealing.

We can normalize this again by subtracking the account's balance from the implemented formula. We just need to decide.

/cc @3esmit @mart1n-xyz

[0x-r4bbit]

We have a certoral rule in the making that currently looks like this:

rule stakingMintsMultiplierPoints1To1Ratio {

  env e;
  uint256 amount;
  uint256 lockupTime;
  uint256 multiplierPointsBefore;
  uint256 multiplierPointsAfter;

  requireInvariant InitialMPIsNeverSmallerThanBalance(e.msg.sender);
  requireInvariant CurrentMPIsNeverSmallerThanInitialMP(e.msg.sender);

  multiplierPointsBefore = getAccountInitialMultiplierPoints(e.msg.sender);
  stake(e, amount, lockupTime);
  multiplierPointsAfter = getAccountInitialMultiplierPoints(e.msg.sender);

  assert lockupTime == 0 => to_mathint(multiplierPointsAfter) == multiplierPointsBefore + amount;
  assert to_mathint(multiplierPointsAfter) >= multiplierPointsBefore + amount;
}

This relies on getAccountInitialMultiplier to really always reflect the initial multiplier points (which is == stakeAmount)

With the current implementation, this breaks. This increasingly seems to ask for initialMP reflecting indeed the initalMP without the increasedMP.

[0x-r4bbit]

Turns out there was a different issue with the rule above, so please ignore the comment.

[mart1n-xyz]

The reason it was done that like in the current code is because if a lockup time is high enough, an account would immediately hit the max boost sealing.

This is a scenario we need to avoid - one should never hit the max boost by locking. I think we can work with the current approach, i.e. initialMP shifts the values by a fixed number and the varying part and limit is taken care of via the bonusMP counter.

However, we need to make sure the following logic is not distorted:

• MPs total (sum of both) is still slashed proportionally on withdrawal and potential subsequent deposits have standard behavior
• locking after a finished lock has standard behavior
• mix of these, plus other scenarios that we haven't discovered

[0x-r4bbit]

We're now always adding the bonusMP (the amount of MP for locking) to the max limit MP (without bonusMP). In other words, `maxPossibleMP = bonusMP + SNT staked * max MP multiplier