many fixes and improvements - rework for modules/ and common/

feat(emailer): add Postmark and Resend providers

backend/Infrastructure/Emailer/Services/ResendEmailSender.cs

@@ -0,0 +1,46 @@
+using System.Net.Http.Headers;
+using System.Text;
+using System.Text.Json;
+using Hutopy.Infrastructure.Emailer.Configuration;
+using Hutopy.Infrastructure.Emailer.Contracts;
+using Microsoft.Extensions.Options;
+
+namespace Hutopy.Infrastructure.Emailer.Services;
+
+public class ResendEmailSender : IEmailSender
+{
+    private static readonly Uri EndpointUri = new("https://api.resend.com/emails");
+    private readonly HttpClient _httpClient;
+    private readonly EmailerOptions _options;
+
+    public ResendEmailSender(
+        IHttpClientFactory httpClientFactory,
+        IOptions<EmailerOptions> options)
+    {
+        _httpClient = httpClientFactory.CreateClient();
+        _options = options.Value;
+
+        _httpClient.DefaultRequestHeaders.Authorization =
+            new AuthenticationHeaderValue("Bearer", _options.ApiKey);
+
+        _httpClient.DefaultRequestHeaders.Accept.Add(
+            new MediaTypeWithQualityHeaderValue("application/json"));
+    }
+
+    public async Task SendEmailAsync(string toEmail, string subject, string htmlMessage)
+    {
+        var payload = new { from = _options.FromEmail, to = toEmail, subject, html = htmlMessage };
+
+        string json = JsonSerializer.Serialize(payload);
+        StringContent content = new(json, Encoding.UTF8, "application/json");
+
+        HttpResponseMessage response = await _httpClient.PostAsync(EndpointUri, content);
+
+        if (!response.IsSuccessStatusCode)
+        {
+            string body = await response.Content.ReadAsStringAsync();
+            throw new InvalidOperationException(
+                $"Resend email failed: {response.StatusCode} - {body}");
+        }
+    }
+}