Merge #958: database: convert CoinStatus to listcoins argument string

fa39e2ced460918d6c6c94c0e2b7dae19b612fa9 database: convert `CoinStatus` to `listcoins` argument string (jp1ac4)

Pull request description:

  This is a preliminary PR towards https://github.com/wizardsardine/liana/issues/677 and is the counterpart to the existing `CoinStatus::from_arg()` method.

  This is needed so that the GUI can pass the required string arguments to the `listcoins` RPC command when using an external Liana daemon.

ACKs for top commit:
  edouardparis:
    ACK fa39e2ced460918d6c6c94c0e2b7dae19b612fa9

Tree-SHA512: e555739e641e4be66ce4942e8294606ab001572395ed73a6c40fa2af38f076357a7c3acba4e4d756fb6d334a11107827a95c53d3f3aecfe32ceca80fc85af83a

src/database/mod.rs

@@ -398,6 +398,17 @@ impl CoinStatus {
             _ => None,
         }
     }
+
+    /// Converts a `CoinStatus` to its equivalent argument name
+    /// as used in the `listcoins` RPC command.
+    pub fn to_arg(&self) -> &'static str {
+        match self {
+            CoinStatus::Unconfirmed => "unconfirmed",
+            CoinStatus::Confirmed => "confirmed",
+            CoinStatus::Spending => "spending",
+            CoinStatus::Spent => "spent",
+        }
+    }
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
@@ -452,3 +463,28 @@ impl LabelItem {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn coin_status_as_arg() {
+        assert_eq!(
+            CoinStatus::from_arg(CoinStatus::Unconfirmed.to_arg()),
+            Some(CoinStatus::Unconfirmed)
+        );
+        assert_eq!(
+            CoinStatus::from_arg(CoinStatus::Confirmed.to_arg()),
+            Some(CoinStatus::Confirmed)
+        );
+        assert_eq!(
+            CoinStatus::from_arg(CoinStatus::Spending.to_arg()),
+            Some(CoinStatus::Spending)
+        );
+        assert_eq!(
+            CoinStatus::from_arg(CoinStatus::Spent.to_arg()),
+            Some(CoinStatus::Spent)
+        );
+    }
+}