Moved some ICurrencyService methods to extensions to simplify use

src/NadekoBot/Services/Currency/CurrencyServiceExtensions.cs

@@ -0,0 +1,28 @@
+using NadekoBot.Services.Currency;
+
+namespace NadekoBot.Services;
+
+public static class CurrencyServiceExtensions
+{
+    public static async Task<long> GetBalanceAsync(this ICurrencyService cs, ulong userId)
+    {
+        await using var wallet = await cs.GetWalletAsync(userId);
+        return await wallet.GetBalance();
+    }
+    
+    public static async Task<bool> TransferAsync(
+        this ICurrencyService cs,
+        ulong fromId,
+        ulong toId,
+        long amount,
+        string fromName,
+        string note)
+    {
+        await using var fromWallet = await cs.GetWalletAsync(fromId);
+        await using var toWallet = await cs.GetWalletAsync(toId);
+
+        var extra = new TxData("gift", fromName, note, fromId);
+
+        return await fromWallet.Transfer(amount, toWallet, extra);
+    }
+}