[PM-1835] Add ForwardEmail alias to Username Generator (#2803)

* Add ForwardEmail alias to Username Generator

* remove unnecessary initializer

* Corrected order of alias Generators

* PM-4307 - Trigger ForwardEmailDomainName PropertyChanged after initialization

src/Core/Services/EmailForwarders/ForwardEmailForwarder.cs

@@ -0,0 +1,52 @@
+using System;
+using System.Net.Http;
+using System.Net.Http.Headers;
+using System.Text;
+using System.Threading.Tasks;
+using Bit.Core.Abstractions;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
+namespace Bit.Core.Services.EmailForwarders
+{
+    public class ForwardEmailForwarderOptions : ForwarderOptions
+    {
+        public string DomainName { get; set; }
+    }
+
+    public class ForwardEmailForwarder : BaseForwarder<ForwardEmailForwarderOptions>
+    {
+        private readonly string _domain;
+        protected override string RequestUri => $"https://api.forwardemail.net/v1/domains/{_domain}/aliases";
+
+        public ForwardEmailForwarder(string domain)
+        {
+            _domain = domain;
+        }
+
+        protected override bool CanGenerate(ForwardEmailForwarderOptions options)
+        {
+            return !string.IsNullOrWhiteSpace(options.ApiKey) && !string.IsNullOrWhiteSpace(options.DomainName);
+        }
+
+        protected override void ConfigureHeaders(HttpRequestHeaders headers, ForwardEmailForwarderOptions options)
+        {
+            headers.Add("Authorization", $"Basic {Convert.ToBase64String(Encoding.UTF8.GetBytes(options.ApiKey + ":"))}");
+        }
+
+        protected override Task<HttpContent> GetContentAsync(IApiService apiService, ForwardEmailForwarderOptions options)
+        {
+            return Task.FromResult<HttpContent>(new StringContent(
+                JsonConvert.SerializeObject(
+                new
+                {
+                    description = "Generated by Bitwarden."
+                }), Encoding.UTF8, "application/json"));
+        }
+
+        protected override string HandleResponse(JObject result)
+        {
+            return $"{result["name"]}@{result["domain"]?["name"] ?? _domain}";
+        }
+    }
+}

src/Core/Services/UsernameGenerationService.cs

@@ -141,6 +141,13 @@ namespace Bit.Core.Services
                                     .GenerateAsync(_apiService, (AnonAddyForwarderOptions)options.GetForwarderOptions());
             }
 
+            if (options.ServiceType == ForwardedEmailServiceType.ForwardEmail)
+            {
+                var forwardedEmailOptions = (ForwardEmailForwarderOptions)options.GetForwarderOptions();
+                return await new ForwardEmailForwarder(forwardedEmailOptions.DomainName)
+                                    .GenerateAsync(_apiService, forwardedEmailOptions);
+            }
+
             BaseForwarder<ForwarderOptions> simpleForwarder = null;
 
             switch (options.ServiceType)