Auth: Handle when access token has already been refreshed in OAuth token sync (#77118)

* Use singleflight to prevent logging error if the token has already been refreshed

* Change order of error checks

* align tests, change error name

* Change sf key

* Update based on the review

* refactor

pkg/services/oauthtoken/oauth_token.go

@@ -173,7 +173,7 @@ func checkOAuthRefreshToken(authInfo *login.UserAuth) error {
 	}
 
 	if authInfo.OAuthRefreshToken == "" {
-		logger.Debug("No refresh token available",
+		logger.Warn("No refresh token available",
 			"authmodule", authInfo.AuthModule, "userid", authInfo.UserId)
 		return ErrNoRefreshTokenFound
 	}