Refactor BTCPay service and API, add lightning balance

app/services/btcpay_manager/fetch_lightning_wallet_balance.rb

@@ -0,0 +1,11 @@
+module BtcpayManager
+  class FetchLightningWalletBalance < BtcpayManagerService
+    def call
+      res = get "stores/#{@store_id}/lightning/BTC/balance"
+
+      {
+        balance: res["offchain"]["local"].to_i / 1000 # msats to sats
+      }
+    end
+  end
+end

app/services/btcpay_manager/fetch_onchain_wallet_balance.rb

@@ -0,0 +1,13 @@
+module BtcpayManager
+  class FetchOnchainWalletBalance < BtcpayManagerService
+    def call
+      res = get "stores/#{@store_id}/payment-methods/onchain/BTC/wallet"
+
+      {
+        balance: (res["balance"].to_f * 100000000).to_i, # BTC to sats
+        unconfirmed_balance: (res["unconfirmedBalance"].to_f * 100000000).to_i,
+        confirmed_balance: (res["confirmedBalance"].to_f * 100000000).to_i
+      }
+    end
+  end
+end