public void Configuration(IAppBuilder app)
        {
            OAuthOptions = new OAuthAuthorizationServerOptions()
                               {
                                   TokenEndpointPath = new PathString("/token"),
                                   Provider = new OAuthAuthorizationServerProvider()
                                                  {
                                                      OnValidateClientAuthentication = async (context) =>
                                                          {
                                                              context.Validated();
                                                          },
                                                      OnGrantResourceOwnerCredentials = async (context) =>
                                                          {
                                                              if (context.UserName == "test.test@mail.com" && context.Password == "test123")
                                                              {
                                                                  ClaimsIdentity oAuthIdentity = new ClaimsIdentity(context.Options.AuthenticationType);
                                                                  context.Validated(oAuthIdentity);
                                                              }
                                                          }
                                                  },
                                   AllowInsecureHttp = true,
                                   AccessTokenExpireTimeSpan = TimeSpan.FromDays(1)
                               };

            app.UseOAuthBearerTokens(OAuthOptions);
        }