decouple transaction payment and currency (#6912)

* wip: setup types

* fix types

* make tx payment pallet independent from balances

* fix dependent tests

* comments

* restructure a bit and  include more info

* clean up ugly phantom

* reduce complexity

* minor doc improvements

* use shorthand

* doc

* fix line lenght and style

* readd BalanceOf

* some clarifications and readability improvements

* move balance type to OnChargeTransaction

* remove noise

* fix style

* Apply suggestions from code review

improved documentation

Co-authored-by: Alexander Theißen <[email protected]>

* Improve naming and documentation

Apply suggestions from code review

Co-authored-by: Alexander Theißen <[email protected]>

* Apply suggestions from code review

Co-authored-by: Kian Paimani <[email protected]>

* always call withdraw_fee

* move NegativeImbalanceOf to payment module

* fix unused import

Co-authored-by: Alexander Theißen <[email protected]>
Co-authored-by: Kian Paimani <[email protected]>

Author: 3 people

src/lib.rs

@@ -491,6 +491,7 @@ mod tests {
 		traits::{Currency, LockIdentifier, LockableCurrency, WithdrawReasons},
 	};
 	use frame_system::{Call as SystemCall, ChainContext, LastRuntimeUpgradeInfo};
+	use pallet_transaction_payment::CurrencyAdapter;
 	use pallet_balances::Call as BalancesCall;
 	use hex_literal::hex;
 	const TEST_KEY: &[u8] = &*b":test:key:";
@@ -632,8 +633,7 @@ mod tests {
 		pub const TransactionByteFee: Balance = 0;
 	}
 	impl pallet_transaction_payment::Trait for Runtime {
-		type Currency = Balances;
-		type OnTransactionPayment = ();
+		type OnChargeTransaction = CurrencyAdapter<Balances, ()>;
 		type TransactionByteFee = TransactionByteFee;
 		type WeightToFee = IdentityFee<Balance>;
 		type FeeMultiplierUpdate = ();