Submitted by hansfriese, also found by 0x52 and codexploder
https://github.com/code-423n4/2022-07-fractional/blob/8f2697ae727c60c93ea47276f8fa128369abfe51/src/modules/Migration.sol#L105
https://github.com/code-423n4/2022-07-fractional/blob/8f2697ae727c60c93ea47276f8fa128369abfe51/src/modules/Migration.sol#L141
Migration.join() and Migration.leave() can still work after unsucessful migration.
As I submitted with my high-risk finding Migration.withdrawContribution() might work unexpectedly after unsuccessful migration., withdraw logic after unsuccessful migration is different from the initial leave() logic and the withdrawal logic would be messy if users call join() and leave() after unsuccessful migration.
According to the explanation, join() and leave() functions must be called for 7 days before commition.
Currently, such a scenario is possible.
Solidity Visual Developer of VSCode
We should add some restrictions to join() and leave() functions so that users can call these functions for 7 days before the migration is committed.
We should add these conditions to join() and leave().
Ferret-san (Fractional) confirmed 
