Refactor Get Store Payment Methods

Add tests + docs + new pluggbale format for fetching payment method data + client

BTCPayServer.Client/Models/OnChainPaymentMethodBaseData.cs

@@ -0,0 +1,24 @@
+using NBitcoin;
+using Newtonsoft.Json;
+
+namespace BTCPayServer.Client.Models
+{
+    public class OnChainPaymentMethodBaseData
+    {
+        /// <summary>
+        /// The derivation scheme
+        /// </summary>
+        public string DerivationScheme { get; set; }
+
+        public string Label { get; set; }
+
+        [JsonConverter(typeof(NBitcoin.JsonConverters.KeyPathJsonConverter))]
+        public RootedKeyPath AccountKeyPath { get; set; }
+
+        public OnChainPaymentMethodBaseData()
+        {
+        }
+
+        
+    }
+}