Proposal Handler for NFT fees

[giorgionocera]

In the nft module, it could be useful to add a new proposal handler to manage a custom proposal that could be used to change the NFTs issuing fees. An example of such a thing could be found in the fantoken module from line 54: https://github.com/bitsongofficial/go-bitsong/blob/84691c819214a1f9b9dd844ea2b49b7ccc8ece1b/x/fantoken/handler.go#L54-L80

[angelorc]

Yes, this is very useful

[ryusmo]

Since nft issue fee is in params, it's not needed to add custom proposal, this can be done with ParamsUpdateProposal with nft subspace in it.

[angelorc]

the specific proposal handler is just a nice to have :) and could be implemented in an hour

we discussed it in our telegram group