Added backend functions

src/WorkTime.Api/Services/AuthService.cs

@@ -0,0 +1,29 @@
+using WorkTime.Shared.Services;
+
+namespace WorkTime.Api.Services;
+
+internal class AuthService(IHttpContextAccessor accessor) : IAuthService {
+    
+    public Task<bool> IsAuthenticated() {
+        var header = accessor.HttpContext?.Request.Headers[IAuthService.HeaderName];
+        if (header is not { Count: 1 })
+            return Task.FromResult(false);
+
+        var value = header.Value[0]!.Replace("Bearer ", "");
+        if (Guid.TryParse(value, out var guid))
+            return Task.FromResult(false);
+
+        return Task.FromResult(guid != Guid.Empty);
+    }
+    
+    public async Task<Guid> GetCurrentUserId() {
+        if (!await IsAuthenticated())
+            return Guid.Empty;
+
+        var header = accessor.HttpContext?.Request.Headers[IAuthService.HeaderName]!;
+        var value = header.Value[0]!.Replace("Bearer ", "");
+        
+        return Guid.Parse(value);
+    }
+    
+}