fix(app): Rename reservedFeeSats to fundingTxFee

The value that we were displaying corresponded to half of the funding
transaction fee.

The fee reserve cannot be derived just by looking at the funding
transaction, as it is included in the funding transaction shared
output. Eventually, we should display the fee reserve in the
corresponding wallet history entry (and perhaps in a channel details
section too).

mobile/lib/features/wallet/domain/wallet_history.dart

@@ -81,7 +81,7 @@ abstract class WalletHistoryItemData {
         amount: amount,
         status: status,
         timestamp: timestamp,
-        reservedFeeSats: Amount(type.reservedFeeSats ?? 0),
+        fundingTxFee: Amount(type.fundingTxFeeSats ?? 0),
         fundingTxid: type.fundingTxid,
         confirmations: type.confirmations,
         ourChannelInputAmountSats: Amount(type.ourChannelInputAmountSats),
@@ -183,7 +183,7 @@ class TradeData extends WalletHistoryItemData {
 }
 
 class DlcChannelFundingData extends WalletHistoryItemData {
-  final Amount reservedFeeSats;
+  final Amount fundingTxFee;
   final String fundingTxid;
   final int confirmations;
   final Amount ourChannelInputAmountSats;
@@ -193,7 +193,7 @@ class DlcChannelFundingData extends WalletHistoryItemData {
       required super.amount,
       required super.status,
       required super.timestamp,
-      required this.reservedFeeSats,
+      required this.fundingTxFee,
       required this.confirmations,
       required this.ourChannelInputAmountSats,
       required this.fundingTxid});

mobile/lib/features/wallet/wallet_history_item.dart

@@ -443,7 +443,7 @@ class DlcChannelFundingHistoryItem extends WalletHistoryItem {
           displayWidget: TransactionIdText(data.fundingTxid)),
       HistoryDetail(label: "Confirmations", value: data.confirmations.toString()),
       HistoryDetail(label: "Channel input", value: formatSats(data.ourChannelInputAmountSats)),
-      HistoryDetail(label: "Reserved fee", value: formatSats(data.reservedFeeSats)),
+      HistoryDetail(label: "Funding TX fee estimate", value: formatSats(data.fundingTxFee)),
     ];
 
     return details;

mobile/native/src/api.rs

@@ -232,7 +232,7 @@ pub enum WalletHistoryItemType {
         funding_txid: String,
         // This fee represents the total fee reserved for all off-chain transactions, i.e. for the
         // fund/buffer/cet/refund. Only the part for the fund tx has been paid for now
-        reserved_fee_sats: Option<u64>,
+        funding_tx_fee_sats: Option<u64>,
         confirmations: u64,
         // The amount we hold in the channel
         our_channel_input_amount_sats: u64,

mobile/native/src/ln_dlc/mod.rs

@@ -479,9 +479,14 @@ fn keep_wallet_balance_and_history_up_to_date(node: &Node) -> Result<()> {
                     status,
                     wallet_type: WalletHistoryItemType::DlcChannelFunding {
                         funding_txid: details.transaction.txid().to_string(),
-                        // this is not 100% correct as fees are not exactly divided by 2. The fee a
-                        // user has to pay depends on his final address.
-                        reserved_fee_sats: details.fee.as_ref().map(|fee| (*fee / 2).to_sat()).ok(),
+                        // this is not 100% correct as fees are not exactly divided by 2. The share
+                        // of the funding transaction fee that the user has paid depends on their
+                        // inputs and change outputs.
+                        funding_tx_fee_sats: details
+                            .fee
+                            .as_ref()
+                            .map(|fee| (*fee / 2).to_sat())
+                            .ok(),
                         confirmations: details.confirmation_status.n_confirmations() as u64,
                         our_channel_input_amount_sats: channel.own_params.collateral,
                     },