Implement basic privacy settings (#392)

* Add ability for clients to submit and retrieve privacy settings data

* Make slot pages and user pages respect user's privacy settings

* Prevent webhook from publishing new levels if user's privacy settings disallow it

* Hide levels/profiles from respective pages depending on privacy settings

* Apply suggestions from review

ProjectLighthouse.Servers.Website/Pages/UsersPage.cshtml.cs

@@ -37,6 +37,7 @@ public class UsersPage : BaseLayout
         if (this.PageNumber < 0 || this.PageNumber >= this.PageAmount) return this.Redirect($"/users/{Math.Clamp(this.PageNumber, 0, this.PageAmount - 1)}");
 
         this.Users = await this.Database.Users.Where(u => !u.Banned && u.Username.Contains(this.SearchValue))
+            .Where(u => u.ProfileVisibility == PrivacyType.All) // TODO: change check for when user is logged in
             .OrderByDescending(b => b.UserId)
             .Skip(pageNumber * ServerStatics.PageSize)
             .Take(ServerStatics.PageSize)