Added endpoint and functionality for getting, retrieving and deleting bookmarks, and for adding and removing tags for a bookmark

YABA.Data/Extensions/UsersDbSetExtensions.cs

@@ -0,0 +1,23 @@
+using Microsoft.EntityFrameworkCore;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using YABA.Models;
+
+namespace YABA.Data.Extensions
+{
+    public static  class UsersDbSetExtensions
+    {
+        public static async Task<bool> UserExistsAsync(this DbSet<User> userDbSet, int userId)
+        {
+            return await userDbSet.AnyAsync(x => x.Id == userId);
+        }
+
+        public static bool UserExists(this DbSet<User> userDbSet, int userId)
+        {
+            return userDbSet.Any(x => x.Id == userId);
+        }
+    }
+}