[PM-25240] Send Access OTP email in MJML format (#6411)

feat: Add MJML email templates for Send Email OTP
feat: Implement MJML-based email templates for Send OTP functionality
feat: Add feature flag support for Send Email OTP v2 emails
feat: Update email view models and call sites for Send Email OTP

fix: Modify the directory structure for MJML templates to have Auth directory for better team ownership
fix: Rename `hero.js` to `mj-bw-hero.js`

---
Co-authored-by: Todd Martin <106564991+trmartin4@users.noreply.github.com>

src/Core/Services/Implementations/HandlebarsMailService.cs

@@ -224,6 +224,27 @@ public class HandlebarsMailService : IMailService
         await _mailDeliveryService.SendEmailAsync(message);
     }
 
+    public async Task SendSendEmailOtpEmailv2Async(string email, string token, string subject)
+    {
+        var message = CreateDefaultMessage(subject, email);
+        var requestDateTime = DateTime.UtcNow;
+        var model = new DefaultEmailOtpViewModel
+        {
+            Token = token,
+            Expiry = "5", // This should be configured through the OTPDefaultTokenProviderOptions but for now we will hardcode it to 5 minutes.
+            TheDate = requestDateTime.ToLongDateString(),
+            TheTime = requestDateTime.ToShortTimeString(),
+            TimeZone = _utcTimeZoneDisplay,
+            WebVaultUrl = _globalSettings.BaseServiceUri.VaultWithHash,
+            SiteName = _globalSettings.SiteName,
+        };
+        await AddMessageContentAsync(message, "Auth.SendAccessEmailOtpEmailv2", model);
+        message.MetaData.Add("SendGridBypassListManagement", true);
+        // TODO - PM-25380 change to string constant
+        message.Category = "SendEmailOtp";
+        await _mailDeliveryService.SendEmailAsync(message);
+    }
+
     public async Task SendFailedTwoFactorAttemptEmailAsync(string email, TwoFactorProviderType failedType, DateTime utcNow, string ip)
     {
         // Check if we've sent this email within the last hour