Rename function explicit to cancellation to cancel

For transitioning to state4 we either go into a redeem or a cancellation scenario.
The function name state4 is misleading, because it is only used for cancellation scenarios.

swap/src/protocol/bob/cancel.rs

@@ -23,8 +23,8 @@ pub async fn cancel(
     force: bool,
 ) -> Result<Result<(Txid, BobState), CancelError>> {
     let state4 = match state {
-        BobState::BtcLocked(state3) => state3.state4(),
-        BobState::XmrLockProofReceived { state, .. } => state.state4(),
+        BobState::BtcLocked(state3) => state3.cancel(),
+        BobState::XmrLockProofReceived { state, .. } => state.cancel(),
         BobState::XmrLocked(state4) => state4,
         BobState::EncSigSent(state4) => state4,
         BobState::CancelTimelockExpired(state4) => state4,

swap/src/protocol/bob/refund.rs

@@ -22,8 +22,8 @@ pub async fn refund(
 ) -> Result<Result<BobState, SwapNotCancelledYet>> {
     let state4 = if force {
         match state {
-            BobState::BtcLocked(state3) => state3.state4(),
-            BobState::XmrLockProofReceived { state, .. } => state.state4(),
+            BobState::BtcLocked(state3) => state3.cancel(),
+            BobState::XmrLockProofReceived { state, .. } => state.cancel(),
             BobState::XmrLocked(state4) => state4,
             BobState::EncSigSent(state4) => state4,
             BobState::CancelTimelockExpired(state4) => state4,

swap/src/protocol/bob/state.rs

@@ -379,7 +379,7 @@ impl State3 {
         .await
     }
 
-    pub fn state4(&self) -> State4 {
+    pub fn cancel(&self) -> State4 {
         State4 {
             A: self.A,
             b: self.b.clone(),

swap/src/protocol/bob/swap.rs

@@ -141,12 +141,12 @@ async fn run_until_internal(
                             }
                         },
                         _ = cancel_timelock_expires => {
-                            let state4 = state3.state4();
+                            let state4 = state3.cancel();
                             BobState::CancelTimelockExpired(state4)
                         }
                     }
                 } else {
-                    let state4 = state3.state4();
+                    let state4 = state3.cancel();
                     BobState::CancelTimelockExpired(state4)
                 };
                 let db_state = state.clone().into();
@@ -188,18 +188,18 @@ async fn run_until_internal(
                                 Err(InsufficientFunds {..}) => {
                                      info!("The other party has locked insufficient Monero funds! Waiting for refund...");
                                      state.wait_for_cancel_timelock_to_expire(bitcoin_wallet.as_ref()).await?;
-                                     let state4 = state.state4();
+                                     let state4 = state.cancel();
                                      BobState::CancelTimelockExpired(state4)
                                 },
                             }
                         },
                         _ = cancel_timelock_expires => {
-                            let state4 = state.state4();
+                            let state4 = state.cancel();
                             BobState::CancelTimelockExpired(state4)
                         }
                     }
                 } else {
-                    let state4 = state.state4();
+                    let state4 = state.cancel();
                     BobState::CancelTimelockExpired(state4)
                 };