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

feat(emailer): add Postmark and Resend providers

backend/Modules/Contents/Models/ContentModel.cs

@@ -0,0 +1,18 @@
+namespace Hutopy.Modules.Contents.Models;
+
+[PublicAPI]
+public class ContentModel
+{
+    public required Guid Id { get; init; }
+    public required Guid CreatedBy { get; init; }
+    public required string CreatedByName { get; init; }
+    public required string? CreatedByPortraitUrl { get; init; }
+    public required DateTimeOffset CreatedAt { get; init; }
+    public Guid? DeletedBy { get; init; } 
+    public DateTimeOffset? DeletedAt { get; init; }
+    public required string Title { get; init; }
+    public required string Description { get; init; }
+    public string HtmlFileUrl { get; init; } = "";
+    public required string[]? Urls { get; init; }
+    public string? ThumbnailUrl { get; init; }
+}

backend/Modules/Contents/Models/FollowModel.cs

@@ -0,0 +1,7 @@
+namespace Hutopy.Modules.Contents.Models;
+
+[PublicAPI]
+public record FollowModel(
+    Guid CreatorId,
+    string CreatorName,
+    string? CreatorPortraitUrl);