• standart timeseries query, 3 fields, timestmap, category_name, metric
• time series panel
• data link var-template_variable_name=${__field.name}

works correctly if we have multiple time series

but works wrong when got only one time series name
used var-template_variable_name=Value, looks like grafana bug, but need to check

If use ${__field.name} in data link, then will work for multiple time series and doesn't work for one time series
If use ${__series.name}, then work for one time series, but doesn't work for multiple

example of data links

/d/${__dashboard.uid}/${__dashboard}?${datasource:queryparam}&${metric:queryparam}&${query_kind:queryparam}&${hostname:queryparam}&${exception_code:queryparam}&${query_hash:queryparam}&${__url_time_range}&var-user=${__field.name}