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

feat(emailer): add Postmark and Resend providers

backend/Modules/Identity/Services/UserLookup.cs

@@ -0,0 +1,21 @@
+using Hutopy.Modules.Identity.Contracts;
+using Hutopy.Modules.Identity.Data;
+
+namespace Hutopy.Modules.Identity.Services;
+
+public sealed class UserLookup(
+    UserManager userManager)
+    : IUserLookup
+{
+    public async Task<UserReference?> GetUserAsync(Guid userId, CancellationToken cancellationToken = default)
+    {
+        var user = await userManager.FindByIdAsync(userId.ToString());
+
+        return user is null
+            ? null
+            : new UserReference(
+                user.Id,
+                user.Fullname,
+                user.PortraitUrl);
+    }
+}