Add receiver removal functionality to SenderEditor

Enhanced the `SenderEditorPage.razor` by injecting the `EnvelopeReceiverService` to manage envelope receivers. Updated the UI to include a remove button for each receiver, invoking the new `RemoveReceiverAsync` method. This method handles the deletion of receivers from both the UI and the server.

Modified `ReceiverDraft` and `SignatureFieldDraft` models to include `ReceiverId` and `ReceiverDraftId` for better tracking. Updated logic for identifying receivers without signature fields and creating receiver commands to use these new identifiers.

Added `DeleteAsync` method in `EnvelopeReceiverService.cs` to send DELETE requests for removing receivers. Updated `envelope-viewer.css` to style the new remove button with distinct appearance and hover effects.

EnvelopeGenerator.Server/EnvelopeGenerator.Server.Client/Services/EnvelopeReceiverService.cs

@@ -4,6 +4,7 @@ using System.Net.Http.Json;
 using System.Text.Json;
 using EnvelopeGenerator.Application.EnvelopeReceivers.Commands.CreateEnvelopeReceiver;
 using EnvelopeGenerator.Server.Client.Models;
+using Microsoft.AspNetCore.WebUtilities;
 
 namespace EnvelopeGenerator.Server.Client.Services;
 
@@ -93,4 +94,31 @@ public class EnvelopeReceiverService(IHttpClientFactory httpClientFactory)
         var payload = await response.Content.ReadFromJsonAsync<ReceiverEnvelopeUrlEnabledResponse>(_jsonOptions, cancel);
         return payload?.Enabled == true;
     }
+
+    public async Task DeleteAsync(int envelopeId, int receiverId, CancellationToken cancel = default)
+    {
+        if (envelopeId <= 0)
+            throw new ArgumentOutOfRangeException(nameof(envelopeId));
+        if (receiverId <= 0)
+            throw new ArgumentOutOfRangeException(nameof(receiverId));
+
+        using var http = httpClientFactory.CreateClient("EnvelopeGenerator.Server");
+        var url = QueryHelpers.AddQueryString("/api/EnvelopeReceiver", new Dictionary<string, string?>
+        {
+            ["EnvelopeId"] = envelopeId.ToString(),
+            ["ReceiverId"] = receiverId.ToString()
+        });
+
+        var response = await http.DeleteAsync(url, cancel);
+        if (response.IsSuccessStatusCode)
+            return;
+
+        var body = await response.Content.ReadAsStringAsync(cancel);
+        var statusCode = (int)response.StatusCode;
+        var reasonPhrase = response.ReasonPhrase ?? "Unknown error";
+        throw new HttpRequestException(
+            $"Failed to remove receiver. Status: {statusCode} ({reasonPhrase}){(string.IsNullOrWhiteSpace(body) ? string.Empty : $" - {body}")}",
+            null,
+            response.StatusCode);
+    }
 }