Show warning when enabling Payjoin but supported payment methods are not using a hot wallet (#1545)

* Show warning when enabling Payjoin but supported payment methods are not using a hot wallet

https://i.imgur.com/RXBhr0n.png fixes #1474

* expose p2p port

BTCPayServer.Tests/docker-compose.yml

@@ -127,6 +127,7 @@ services:
         deprecatedrpc=signrawtransaction
     ports: 
       - "43782:43782"
+      - "39388:39388"
     expose:
       - "43782" # RPC
       - "39388" # P2P

BTCPayServer/Controllers/StoresController.cs

@@ -30,6 +30,7 @@ using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.Rendering;
 using NBitcoin;
 using NBitcoin.DataEncoders;
+using NBXplorer;
 
 namespace BTCPayServer.Controllers
 {
@@ -545,6 +546,7 @@ namespace BTCPayServer.Controllers
                 Provider = "CoinSwitch"
             });
         }
+        
 
         [HttpPost]
         [Route("{storeId}")]
@@ -574,6 +576,7 @@ namespace BTCPayServer.Controllers
             blob.InvoiceExpiration = model.InvoiceExpiration;
             blob.LightningDescriptionTemplate = model.LightningDescriptionTemplate ?? string.Empty;
             blob.PaymentTolerance = model.PaymentTolerance;
+            var payjoinChanged = blob.PayJoinEnabled != model.PayJoinEnabled;
             blob.PayJoinEnabled = model.PayJoinEnabled;
             if (CurrentStore.SetStoreBlob(blob))
             {
@@ -583,7 +586,31 @@ namespace BTCPayServer.Controllers
             if (needUpdate)
             {
                 await _Repo.UpdateStore(CurrentStore);
+                
                 TempData[WellKnownTempData.SuccessMessage] = "Store successfully updated";
+
+                if (payjoinChanged && blob.PayJoinEnabled)
+                {
+                    var problematicPayjoinEnabledMethods = CurrentStore.GetSupportedPaymentMethods(_NetworkProvider)
+                        .OfType<DerivationSchemeSettings>()
+                        .Where(settings =>
+                            settings.Network.SupportPayJoin &&
+                            string.IsNullOrEmpty(_ExplorerProvider.GetExplorerClient(settings.Network)
+                                .GetMetadata<string>(settings.AccountDerivation,
+                                    WellknownMetadataKeys.Mnemonic)))
+                        .Select(settings => settings.PaymentId.CryptoCode)
+                        .ToArray();
+
+                    if (problematicPayjoinEnabledMethods.Any())
+                    {
+                        TempData.Remove(WellKnownTempData.SuccessMessage);
+                        TempData.SetStatusMessageModel(new StatusMessageModel()
+                        {
+                            Severity = StatusMessageModel.StatusSeverity.Warning,
+                            Html = $"The store was updated successfully. However, payjoin will not work for {string.Join(", ", problematicPayjoinEnabledMethods)} until you configure them to be a <a href='https://docs.btcpayserver.org/features/wallet/hotwallet' class='alert-link' target='_blank'>hot wallet</a>."
+                        });
+                    }
+                }
             }
 
             return RedirectToAction(nameof(UpdateStore), new