override conversion rate in estimate-message-fee RPC (#1189)

bridges/primitives/chain-kusama/src/lib.rs

@@ -24,6 +24,7 @@ use bp_messages::{LaneId, MessageDetails, MessageNonce, UnrewardedRelayersState}
 use frame_support::weights::{
 	WeightToFeeCoefficient, WeightToFeeCoefficients, WeightToFeePolynomial,
 };
+use sp_runtime::FixedU128;
 use sp_std::prelude::*;
 use sp_version::RuntimeVersion;
 
@@ -141,6 +142,7 @@ sp_api::decl_runtime_apis! {
 		fn estimate_message_delivery_and_dispatch_fee(
 			lane_id: LaneId,
 			payload: OutboundPayload,
+			kusama_to_this_conversion_rate: Option<FixedU128>,
 		) -> Option<OutboundMessageFee>;
 		/// Returns dispatch weight, encoded payload size and delivery+dispatch fee of all
 		/// messages in given inclusive range.