Removed some dead code on the interfaces. Introduced UnitOfWork to simplify repo injection.

API/Data/UnitOfWork.cs

@@ -0,0 +1,36 @@
+using System.Threading.Tasks;
+using API.Entities;
+using API.Interfaces;
+using AutoMapper;
+using Microsoft.AspNetCore.Identity;
+
+namespace API.Data
+{
+    public class UnitOfWork : IUnitOfWork
+    {
+        private readonly DataContext _context;
+        private readonly IMapper _mapper;
+        private readonly UserManager<AppUser> _userManager;
+
+        public UnitOfWork(DataContext context, IMapper mapper, UserManager<AppUser> userManager)
+        {
+            _context = context;
+            _mapper = mapper;
+            _userManager = userManager;
+        }
+
+        public ISeriesRepository SeriesRepository => new SeriesRepository(_context, _mapper);
+        public IUserRepository UserRepository => new UserRepository(_context, _mapper, _userManager);
+        public ILibraryRepository LibraryRepository => new LibraryRepository(_context, _mapper);
+        
+        public async Task<bool> Complete()
+        {
+            return await _context.SaveChangesAsync() > 0;
+        }
+
+        public bool HasChanges()
+        {
+            return _context.ChangeTracker.HasChanges();
+        }
+    }
+}