feat (pop api): add burn and mint to local fungibles use case

[Daanvdplas]

Based on the Mintable and Burnable standards.

standards:

• mint
• burn

As you can see they also emit the Transfer event

[chungquantin]

• Reference for native token: https://substrate.stackexchange.com/questions/1071/is-there-any-way-to-mint-new-native-tokens-after-deploying-the-substrate-chain
• With non-native fungible asset, we can basically call the dispatchable functions directly

#[pallet::call_index(6)]
pub fn mint(
	origin: OriginFor<T>,
	id: T::AssetIdParameter,
	beneficiary: AccountIdLookupOf<T>,
	#[pallet::compact] amount: T::Balance,
) -> DispatchResult

#[pallet::call_index(7)]
pub fn burn(
	origin: OriginFor<T>,
	id: T::AssetIdParameter,
	who: AccountIdLookupOf<T>,
	#[pallet::compact] amount: T::Balance,
) -> DispatchResult

[Daanvdplas]

For the native token we won't be able to mint or burn since we are using the DOT token. Minting happens through inflation.

In other words, we need Polkadot root origin to do that which we can not :)

This is a good find, we will have to look for what error to return (BadOrigin perhaps) and make sure this is documented properly in the API.

[chungquantin]

@Daanvdplas But this is specifically in the Pop network case that use DOT as a chain token right? I think POP API still need to support the native token mint when it is used in other Substrate-based blockchain.

[Daanvdplas]

This will still require the root origin most of the time because allowing anyone to mint the native token of the chain seems like a unlikely configuration (difficult to create value for your token if everyone can create them our of thin air). A chain using a contract to mint its native token could be a use case but TMO not reason enough to include it now. In general, the force_ dispatchables have also not been added to the fungibles use case for the same reason. Depending on use cases and developer demand we can always implement them.

[Daanvdplas]

Closed with #150