add support for postal and multi service mail delivery (#1326)

* adds suppose for postal and multi service mail delivery

* adjust tags

* dont need settings checks in multi-service

src/Core/Services/Implementations/MultiServiceMailDeliveryService.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Threading.Tasks;
+using Microsoft.Extensions.Logging;
+using Bit.Core.Settings;
+using Microsoft.AspNetCore.Hosting;
+using System.Net.Http;
+using Bit.Core.Models.Mail;
+
+namespace Bit.Core.Services
+{
+    public class MultiServiceMailDeliveryService : IMailDeliveryService
+    {
+        private readonly IMailDeliveryService _sesService;
+        private readonly IMailDeliveryService _postalService;
+        private readonly int _postalPercentage;
+
+        private static Random _random = new Random();
+
+        public MultiServiceMailDeliveryService(
+            GlobalSettings globalSettings,
+            IWebHostEnvironment hostingEnvironment,
+            IHttpClientFactory httpClientFactory,
+            ILogger<AmazonSesMailDeliveryService> sesLogger,
+            ILogger<PostalMailDeliveryService> postalLogger)
+        {
+            _sesService = new AmazonSesMailDeliveryService(globalSettings, hostingEnvironment, sesLogger);
+            _postalService = new PostalMailDeliveryService(globalSettings, postalLogger, hostingEnvironment,
+                httpClientFactory);
+
+            // 2% by default
+            _postalPercentage = (globalSettings.Mail?.PostalPercentage).GetValueOrDefault(2);
+        }
+
+        public async Task SendEmailAsync(MailMessage message)
+        {
+            var roll = _random.Next(0, 99);
+            if (roll < _postalPercentage)
+            {
+                await _postalService.SendEmailAsync(message);
+            }
+            else
+            {
+                await _sesService.SendEmailAsync(message);
+            }
+        }
+    }
+}