Implement optimistic locking for read-update-write swap operations (#652)

* Implement optimistic locking for read-update-write swap operations

* Fail on stale swap update and add tests

lib/core/src/test_utils/chain_swap.rs

@@ -137,6 +137,7 @@ pub(crate) fn new_chain_swap(
                 }
             }"#
             .to_string(),
+            version: 0
         };
     }
     match direction {
@@ -223,6 +224,7 @@ pub(crate) fn new_chain_swap(
                     }
                 }
             }"#.to_string(),
+            version: 0,
         },
         Direction::Outgoing => ChainSwap {
             id: generate_random_string(4),
@@ -306,6 +308,7 @@ pub(crate) fn new_chain_swap(
                     }
                 }
             }"#.to_string(),
+            version: 0
         }
     }
 }

lib/core/src/test_utils/persist.rs

@@ -86,6 +86,7 @@ pub(crate) fn new_send_swap(payment_state: Option<PaymentState>) -> SendSwap {
         created_at: utils::now(),
         state: payment_state.unwrap_or(PaymentState::Created),
         refund_private_key: "945affeef55f12227f1d4a3f80a17062a05b229ddc5a01591eb5ddf882df92e3".to_string(),
+        version: 0,
     }
 }
 
@@ -140,6 +141,7 @@ pub(crate) fn new_receive_swap(payment_state: Option<PaymentState>) -> ReceiveSw
         mrh_tx_id: None,
         created_at: utils::now(),
         state: payment_state.unwrap_or(PaymentState::Created),
+        version: 0,
     }
 }