Standard or minimum transaction fee

[kwunyeung]

Feature description

Be default, Cosmos-SDK let full nodes to define their min-gas-prices. This would lead to Desmos have a chance of facing zero-fee spam attack. I think we have to setup a minimum or standard fee structure for different Posts and Reports message types. We should not let users be able to post, make reactions or report without any fee. We can keep the way how other StdTx is working but only keeps transactions in Posts and Reports module have such constraints.

IRISnet has a standard minimum fee and e-Money has a PoA configurable minimum fee. I think we can learn how they are doing. While we are still studying the tokenomics and usage of a secondary fee token, we can first test this mechanism with the testing udaric. There is a module based AnteDecorator in the SDK for customizing the AnteHandler. Can this be achieved by making use of it?

[RiccardoM]

@kwunyeung Yes, this can be easily achieved using the AnteDecorator and making sure that a min fee is included if the transaction contains one of the above mentioned message types.

Do we have any idea on the min fee to be paid for each message?

[kwunyeung]

We can keep the current testing amount 0.01 Daric first.