New API endpoint: Send email using store SMTP (#3181)

Co-authored-by: Kukks <evilkukka@gmail.com>

BTCPayServer/Controllers/GreenField/GreenfieldStoreEmailController.cs

@@ -0,0 +1,47 @@
+#nullable enable
+using System;
+using System.Threading.Tasks;
+using BTCPayServer.Abstractions.Constants;
+using BTCPayServer.Abstractions.Extensions;
+using BTCPayServer.Client;
+using BTCPayServer.Client.Models;
+using BTCPayServer.Services.Mails;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Cors;
+using Microsoft.AspNetCore.Mvc;
+
+namespace BTCPayServer.Controllers.GreenField
+{
+    [ApiController]
+    [Authorize(AuthenticationSchemes = AuthenticationSchemes.Greenfield)]
+    [EnableCors(CorsPolicies.All)]
+    public class GreenfieldStoreEmailController : Controller
+    {
+        private readonly EmailSenderFactory _emailSenderFactory;
+
+        public GreenfieldStoreEmailController(EmailSenderFactory  emailSenderFactory)
+        {
+            _emailSenderFactory = emailSenderFactory;
+        }
+        
+        [Authorize(Policy = Policies.CanModifyStoreSettings, AuthenticationSchemes = AuthenticationSchemes.Greenfield)]
+        [HttpPost("~/api/v1/stores/{storeId}/email/send")]
+        public async Task<IActionResult> SendEmailFromStore(string storeId,
+            [FromBody] SendEmailRequest request)
+        {
+            var store = HttpContext.GetStoreData();
+            if (store == null)
+            {
+                return this.CreateAPIError(404, "store-not-found", "The store was not found");
+            }
+            var emailSender = await _emailSenderFactory.GetEmailSender(storeId);
+            if (emailSender is null )
+            {
+                return this.CreateAPIError(404,"smtp-not-configured", "Store does not have an SMTP server configured.");
+            }
+            
+            emailSender.SendEmail(request.Email, request.Subject, request.Body);
+            return Ok();
+        }
+    }
+}