TODOs with priority

1. [x] deposit token: https://github.com/Fluidex/contracts/issues/1
2. [ ] block verification & submission: https://github.com/Fluidex/contracts/issues/11
2. [ ] proxy and Upgradeable pattern: https://github.com/Fluidex/contracts/issues/2
3. [x] migration & deployment tools: https://github.com/Fluidex/contracts/issues/3
4. [ ] registerWithdrawal: https://github.com/Fluidex/contracts/issues/19