[Discussion] Use min_commission_rate Instead of ValidatorCommissionDecorator

[dongsam]

Background:

• The latest version of the SDK's staking module params includes min_commission_rate.
• Both the existing ValidatorCommissionDecorator of antehandler logic and the newly introduced min_commission_rate in the SDK staking module params perform the same function: they validate the minimum commission rate during the Create and Edit validator processes. Ref1, Ref2.

Suggestions:

• antehandler adds complexity due to nested msg processing like authz, performing unnecessary validations on all transactions. Simplifying this process is recommended.
• Without specific reasons against it, using min_commission_rate is advised for its simplicity and manageability. Moreover, as this parameter is governed not hardcoded, it can be easily modified through governance proposals in the future.

Action Items:
If the decision is made to use min_commission_rate instead of antehandler:

1. Remove ValidatorCommissionDecorator from the antehandler.
2. Set the initial value of min_commission_rate in the upgrade handler.

This will be incorporated in the ongoing SDK v50 bump PR b-harvest#53