feat(cketh): burn ckETH from the minter's own fee subaccount

rs/ethereum/cketh/minter/src/ledger_client.rs

@@ -71,12 +71,36 @@ impl LedgerClient {
         from: Account,
         amount: A,
         memo: BurnMemo,
+    ) -> Result<LedgerBurnIndex, LedgerBurnError> {
+        self.burn_from_with_spender(from, None, amount, memo).await
+    }
+
+    pub async fn burn_from_own_subaccount<A: Into<Nat>>(
+        &self,
+        subaccount: [u8; 32],
+        amount: A,
+        memo: BurnMemo,
+    ) -> Result<LedgerBurnIndex, LedgerBurnError> {
+        let from = Account {
+            owner: ic_cdk::api::canister_self(),
+            subaccount: Some(subaccount),
+        };
+        self.burn_from_with_spender(from, Some(subaccount), amount, memo)
+            .await
+    }
+
+    async fn burn_from_with_spender<A: Into<Nat>>(
+        &self,
+        from: Account,
+        spender_subaccount: Option<[u8; 32]>,
+        amount: A,
+        memo: BurnMemo,
     ) -> Result<LedgerBurnIndex, LedgerBurnError> {
         let amount = amount.into();
         match self
             .client
             .transfer_from(TransferFromArgs {
-                spender_subaccount: None,
+                spender_subaccount,
                 from,
                 to: ic_cdk::api::canister_self().into(),
                 amount: amount.clone(),

rs/ethereum/cketh/minter/src/lib.rs

@@ -45,3 +45,10 @@ pub const EVM_RPC_ID_PRODUCTION: Principal =
     Principal::from_slice(&[0, 0, 0, 0, 2, 48, 0, 204, 1, 1]);
 pub const EVM_RPC_ID_STAGING: Principal = Principal::from_slice(&[0, 0, 0, 0, 2, 48, 0, 161, 1, 1]);
 pub const CKETH_LEDGER_MEMO_SIZE: u16 = 80;
+
+pub const CKETH_FEE_SUBACCOUNT: [u8; 32] = {
+    let mut subaccount = [0_u8; 32];
+    subaccount[30] = 0x0f;
+    subaccount[31] = 0xee;
+    subaccount
+};