add some debug logging to user info request validator for server side…

… sessions

src/IdentityServer/Validation/Default/UserInfoRequestValidator.cs

@@ -99,13 +99,15 @@ public async Task<UserInfoRequestValidationResult> ValidateRequestAsync(string a
 
                 if (sessions.Count == 1)
                 {
+                    _logger.LogDebug("Loading subject claims from server-side session store");
                     subject = sessions.First().AuthenticationTicket.Principal;
                 }
             }
         }
 
         if (subject == null)
         {
+            _logger.LogDebug("Loading subject claims from access token");
             // this falls back to prior behavior which provides the best we can for the subject based on claims from the access token
             var claims = tokenResult.Claims.Where(x => !Constants.Filters.ProtocolClaimsFilter.Contains(x.Type));
             subject = Principal.Create("UserInfo", claims.ToArray());