Abstraction of the base asset

[Chralt98]

Related to #100.

The aim is to use only the MultiCurrency trait for the prediction market pallet instead of directly calling the balances pallet.

Therefore it's easier to use a different base asset (like aUSD) later.

[Chralt98]

In the runtime the only occurrence of the orml_currencies pallet is the swaps pallet here.

I would assume, that the correct abstraction of the base asset is to use the orml_currencies as Shares here in the prediction market pallet. As I understand it correctly the orml_tokens lets us to handle multiple currencies (for us outcome tokens / assets) and the orml_currencies lets us conveniently handle all the functionality of orml_tokens plus the functionality to manage the NativeCurrency with the BasicCurrencyAdapter.

But there is a problem, that the new NamedMultiReservableCurrency trait isn't allowed to use as a MultiCurrency in the orml_currencies pallet yet. I opened an issue for that here.

[Chralt98]

At the moment I use T::BaseAsset::get() which is initialised with the GetNativeCurrency at the moment. But it's later much easier to enter it in each extrinsic as a call parameter.

[maltekliemann]

Good stuff! 👍

I guess the next step is to add a base_asset field to the Market primitive and replace ZTG with the market's base_asset where appropriate?

[maltekliemann]

👍

[sea212]

Looks great overall, thanks for paving the way to using other chains assets within the prediction markets. Can't await the moment when the first external token enters a market!

[sea212]

I am fine with that, we'll handle treasury deposits a bit later down the line.

[sea212]

I'll have a look and approve eventually after overflow handling was applied and main was merge into this.