Add fee for issuing credits and burn fee upon issuance

[ryanchristo]

Summary

@glandua requested that we look into a fee for issuing credits. The fee would be burned in the same way that the credit class and basket creation fee are burned.

This relates to #1314 but could be implemented separately. We have two messages that this might relate to, MsgCreateBatch and MsgMintBatchCredits. If the fee is not something that is decided upon at the credit class level (#1314), we would need to add a new governance parameter and proposal for credit issuance fee.

One question to keep in mind, especially in regards to MsgMintBatchCredits, is how this would affect bridging credits from another chain and whether the issuer (the bridge service) would be responsible for paying this fee.

Problem Definition

[ work in progress ]

Proposal

[ work in progress ]

---

For Admin Use

• Not duplicate issue
• Appropriate labels applied
• Appropriate contributors tagged
• Contributor assigned/self-assigned

[glandua]

I think the bridge service should be responsible for the fees, and in the case of the upcoming Toucan bridge RND can talk to Toucan and ensure the bridge service is funded to pay for this.