fix(backend): make API types internal

backend/src/Socialize.Api/Modules/ContentItems/Handlers/CreateContentItem.cs

@@ -10,7 +10,7 @@ using System.Text.Json;
 
 namespace Socialize.Api.Modules.ContentItems.Handlers;
 
-public record CreateContentItemRequest(
+internal record CreateContentItemRequest(
     Guid WorkspaceId,
     Guid ClientId,
     Guid CampaignId,
@@ -20,7 +20,7 @@ public record CreateContentItemRequest(
     string? Hashtags,
     DateTimeOffset? DueDate);
 
-public class CreateContentItemRequestValidator
+internal class CreateContentItemRequestValidator
     : Validator<CreateContentItemRequest>
 {
     public CreateContentItemRequestValidator()
@@ -35,7 +35,7 @@ public class CreateContentItemRequestValidator
     }
 }
 
-public class CreateContentItemHandler(
+internal class CreateContentItemHandler(
     AppDbContext dbContext,
     AccessScopeService accessScopeService,
     IContentItemActivityWriter activityWriter,