Have minimum commission rate

[youngjoon-lee]

For healthier validator/delegator ecosystem, we can try to introduce the minimum commission rate.

• Cosmos SDK x/staking module must have a min_commssion_rate param.
  • Osmosis has already done this work by forking https://github.com/cosmos/cosmos-sdk as https://github.com/osmosis-labs/cosmos-sdk.
  • Similarly, I've already done it as feat: add minimum commission rate to x/staking cosmos-sdk#27
• panacea-core should have an upgrade handler which updates validator commissions that is smaller than min_commission_rate.
  • References
    • Min Commission Rate osmosis-labs/osmosis#184
    • Change upgrade name, add auto-updating validator commission rates osmosis-labs/osmosis#353
• Write a signaling proposal for setting min_commission_rate to 3% initially as Hojin suggested. She said that 5% may be considered too dramatic because we already started without any limitation.
  • Share this proposal to participants and open a on-chain governance after semi-consensus is made with participants.

[youngjoon-lee]

released as v2.0.3